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501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear...

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1 www.ice77.net Oscillators Oscillators are electronic circuits that produce a constant oscillating signal that can be a sinusoid, a square wave or a triangular wave. Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a. RC Wien bridge Phase shift Twin-T Quadrature Robinson b. LC Armstrong/Meissner Hartley Colpitts Gouriet/Clapp Vackář Cross-coupled Meacham bridge Seiler c. Crystal Pierce Butler 2. Negative resistance Oscillators are classified as nonlinear or relaxation oscillators if their output is a square, a sawtooth or a triangular waveform. 1. Multivibrators a. Astable b. Monostable c. Bistable 2. Ring 3. Pearson-Anson or neon lamp 4. Delay line 5. Royer Some oscillators are simply classified as generators and their output is a square or a triangular waveform: 6. Square wave generator 7. Square/triangle waves generator 8. Triangle/square waves generator
Transcript
Page 1: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

1 www.ice77.net

Oscillators Oscillators are electronic circuits that produce a constant oscillating signal that can be a sinusoid, a square wave or a triangular wave. Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a. RC Wien bridge Phase shift Twin-T Quadrature Robinson b. LC Armstrong/Meissner Hartley Colpitts Gouriet/Clapp Vackář Cross-coupled Meacham bridge Seiler c. Crystal Pierce Butler 2. Negative resistance Oscillators are classified as nonlinear or relaxation oscillators if their output is a square, a sawtooth or a triangular waveform. 1. Multivibrators a. Astable b. Monostable c. Bistable 2. Ring 3. Pearson-Anson or neon lamp 4. Delay line 5. Royer Some oscillators are simply classified as generators and their output is a square or a triangular waveform: 6. Square wave generator 7. Square/triangle waves generator 8. Triangle/square waves generator

Page 2: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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Notes:

Oscillators such as Hartley, Colpitts and Gouriet/Clapp can be configured to be Voltage-Controlled Oscillators (VCO). The frequency of the oscillators depends on input voltage.

The Vackář oscillator is described as a Variable-Frequency Oscillator (VFO).

Its frequency can be tuned with a variable capacitor. Its output is nearly constant over its frequency range of operation.

. Crystal oscillators were developed in the 1920s and 1930s and provided

better frequency stability than tuned oscillators because they are affected by temperature to a much lower degree (they are more stable).

The Tri-tet oscillator is described as an Electron-Coupled Oscillator (ECO).

Page 3: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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RC oscillators RC oscillators contain resistors and capacitors. They are typically used for low frequency (audio range or up to 20kHz). Wien bridge oscillator The circuit was first conceived by Prussian physicist Max Wien in 1891. Because of limitations during his time, the circuit was not constructed until American engineer William Hewlett revisited it in 1939 for his master’s degree thesis. Shortly after that, Hewlett-Packard was founded and one of the company’s first products was a sine-wave oscillator based on the Wien bridge circuit. The final product proved to be very successful and it became very popular because it was stable and inexpensive.

U1

AD741

+3

-2

V+7

V-4

OUT6

OS11

OS25

R3

57

C2

22n

C1

22n

0

0

0 0

V2

10Vdc

V1

10Vdc

0

V+V-

V+

V-

R2

1k

R4

115

R1

1k

V

Wien bridge oscillator

The Wien bridge oscillator uses positive feedback which is provided by a bandpass filter made up by two RC circuits, one in parallel (R1 and C1) and one in series (R2 and C2). R4 is a variable resistor and R3, at the time of Hewlett, was a light bulb.

Time

100.00ms 100.05ms 100.10ms 100.15ms 100.20ms 100.25ms 100.30ms 100.35ms 100.40ms 100.45ms 100.50msV(U1:OUT)

-5.0V

0V

5.0V

Transient response of the Wien bridge oscillator

Page 4: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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The ideal set of parameters is the following:

RRR 21 CCC 21 1

2

3

4 R

R

R3, the light bulb, has a selected resistance:

573R

The value for R4 can be easily calculated:

1142 34 RR

The gain is given by the following expression:

32157

11411

3

4

R

R

V

VA

i

o

The oscillating frequency is:

kHznFkRC

f 234.72212

1

2

1

The oscillating frequency from the simulation is 6.896kHz. Note: modern Wien bridge oscillators use other nonlinear elements such as diodes, thermistors, field effect transistors or photocells in place of light bulbs.

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Quadrature oscillator This circuit uses positive and negative feedback to generate two sinusoidal waves of similar properties, one of them being a sine and the other one being a cosine. C1 through C3 must be matched. All resistors should also be matched, except for R1 which must be slightly less than R2 and R3 to cause the circuit to oscillate. D1 through D4 avoid clipping at the outputs (breakdown voltage is 8.1V).

V1 10Vdc V2 10Vdc

0 0

V-V+

V-

V+

U1

uA741

+3

-2

V+7

V-

4

OUT6

OS11

OS25

V-U2

uA741

+3

-2

V+7

V-

4

OUT6

OS11

OS25

V+

R3

1k

R2

1k

C3

1u

C1

1uC2

1u

0

0

COSINE

SINE

Dbreak

D2

Dbreak

D4Dbreak

D1

Dbreak

D3

R1

900

0

V

V

Quadrature oscillator

Time

2.980s 2.982s 2.984s 2.986s 2.988s 2.990s 2.992s 2.994s 2.996s 2.998s 3.000sV(D2:2) V(D4:2)

-10V

-5V

0V

5V

10V

Transient response of the quadrature oscillator

The oscillating frequency is:

HzRC

f 1592

1

where R=R2=R3 and C=C1=C2=C3. The oscillating frequency from the simulation is 161Hz.

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LC oscillators

LC oscillators contain inductors and capacitors. They are typically used for high frequency (radio range or above 20kHz). Hartley oscillator This circuit was invented by American engineer Ralph Vinton Lyon Hartley in 1915. The oscillating frequency of this circuit depends on L1, L2 and C1. The Hartley oscillator is the dual circuit of the Colpitts oscillator which follows next.

Q1

Q2N2222

R1

100k

C3

100nF

V1

10Vdc

L1

142.5uH

L2

15.8uH

C2

100nF

R2

20k

0

R3

2.2kC1

4nF

0

0

C4

100nF

R4

10k

V

V

Hartley oscillator

Time

24.980ms 24.982ms 24.984ms 24.986ms 24.988ms 24.990ms 24.992ms 24.994ms 24.996ms 24.998ms 25.000msV(R4:2) V(C4:1)

-10V

0V

10V

Transient response of the Hartley oscillator

Page 7: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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If the inductors are not coupled, L is given by:

21 LLL If the inductors are coupled, L is given by:

2121 LLkLLL

where k is the coupling coefficient, a number between 0 and 1. The oscillating frequency for the circuit is given by:

kHznFHLC

f 009.20043.1582

1

2

1

1

The oscillating frequency from the simulation is 200kHz.

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Colpitts oscillator This circuit was invented by American engineer Edwin Henry Colpitts in 1918. The oscillating frequency of this circuit depends on C1, C2 and L1. The Colpitts oscillator is the dual circuit of the Hartley oscillator discussed above.

V

V

Q1

Q2N2222

R1

100k

C3

100nF

R2

20k R3

2.2k

C1

40nF

C2

400nF

V1

10Vdc

0

0

0

L1

17.41uHC4

100nF

R4

10k

Colpitts oscillator

Time

24.980ms 24.982ms 24.984ms 24.986ms 24.988ms 24.990ms 24.992ms 24.994ms 24.996ms 24.998ms 25.000msV(V1:+) V(R4:1)

0V

5V

10V

15V

Transient response of the Colpitts oscillator

Page 9: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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The oscillating frequency for the circuit is given by:

kHz

nFnF

nFnFH

CC

CCL

f 026.200

40040

4004041.172

1

2

1

21

211

The oscillating frequency from the simulation is 200kHz.

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Gouriet/Clapp oscillator This circuit was independently discovered and first published by American electrical engineer James Kilton Clapp in 1948. However, the circuit was invented by Geoffrey George Gouriet and it was used as early as 1938 at the BBC but this was not made public until after World War II due to the fact the circuit was kept secret. Essentially, the Gourier-Clapp oscillator is a Colpitts oscillator with an additional capacitor in series with the inductor.

R4

10k

C3

1uF

0

R5

100Meg

V

V

Q1

Q2N2222

R1

100k

C4

100nF

R2

20kR3

2.2k

C1

100nF

C2

1uF

V1

9Vdc

0

L1

10uH

C5

100nF

0

Gouriet-Clapp oscillator

Note: R5 is placed to force PSpice A/D to start.

Time

29.980ms 29.982ms 29.984ms 29.986ms 29.988ms 29.990ms 29.992ms 29.994ms 29.996ms 29.998ms 30.000msV(V1:+) V(L1:1)

0V

4V

8V

12V

Transient response of the Gouriet-Clapp oscillator

Page 11: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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The oscillating frequency for the circuit is given by:

kHzFFnFFCCCL

f 346.1741

1

1

1

100

1

10

1

2

11111

2

1

3211

The oscillating frequency from the simulation is 166.666kHz.

Page 12: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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Vackář oscillator This circuit was published in a paper by Czech engineer Jiří Vackář in 1949 but he attributed the invention of the oscillator that dates back to 1945 to a firm called Radioslava in Czechoslovakia.

L2

6.2uH

L1

100uH

C1100pF

C2600pF

C37.2nF

C41nF

V1

5Vdc

00

J1

J2N3819

V

V

Vackář oscillator

Time

4.9980ms 4.9982ms 4.9984ms 4.9986ms 4.9988ms 4.9990ms 4.9992ms 4.9994ms 4.9996ms 4.9998ms 5.0000msV(V1:+) V(C1:2)

-25V

0V

25V

50V

Transient response of the Vackář oscillator

The oscillating frequency from the simulation is 2MHz.

Page 13: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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Multivibrators Multivibrators are circuits designed to implement a two-state logic system and they can be of three types: astable, monostable and bistable. Astable multivibrators constantly oscillate between two states. Monostable multivibrators can be placed in a transient state by an external signal and return to the initial stable state after a specific time. Bistable multivibrators stay in either of two stable states and alternate between them depending on an external trigger. Astable multivibrator This circuit constantly oscillates between two states.

R11k

R268k

R382k

R41k

C1

100nF

C2

150nF

0

VCC

VCC

0

V1

5Vdc

Q1

Q2N2222

Q2

Q2N2222

++ --

VV

Astable multivibrator

Time

0s 10ms 20ms 30ms 40ms 50ms 60ms 70ms 80ms 90ms 100msV(C2:2)

0V

2.5V

5.0VV(C1:1)

0V

2.5V

5.0V

SEL>>

Transient response of the astable multivibrator

Page 14: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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The astable multivibrator frequency depends on the values of R2, C1, R3 and C2:

HznFknFkCRCRT

f 534.7515082100682ln

1

2ln

11

2312

The frequency from the simulation is 72.49Hz. As shown in the simulation, the circuit oscillates between two states. Note: if R2=R3 and C1=C2 the duty cycle will be exactly 50%.

Page 15: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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Monostable multivibrator This circuit can be placed in a transient state by an external signal and return to the initial stable state after a specific time.

R11k

R25k

R41k

C1

600nF

0

VCC

VCC

0

V1

5Vdc

Q1

Q2N2222

Q2

Q2N2222

+ R3

68k

V2

TD = 20ms

TF = 10nsPW = 30msPER = 100ms

V1 = 0.7V

TR = 10ns

V2 = 0V

0

-

V

VV

Monostable multivibrator

Time

0s 10ms 20ms 30ms 40ms 50ms 60ms 70ms 80ms 90ms 100msV(C1:1) V(R3:1)

0V

2.5V

5.0V

V(C1:2)

250mV

500mV

750mV

-100mVSEL>>

Transient response of the monostable multivibrator

Page 16: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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As shown in the simulation, Q2 is initially on and Q1 is off. External signal V2 brings the base of Q2 down to 0V which turns off Q2 and turns on Q1. When V2 goes back up to 0.7V the circuits goes back to its initial state. The time the monostable multivibrator stays in the transient state depends on the values of R2 and C1:

msnFkCRt 079.260052ln2ln 12

Time

49.0ms 49.5ms 50.0ms 50.5ms 51.0ms 51.5ms 52.0ms 52.5ms 53.0msV(C1:1) V(R3:1)

2.5V

5.0V

-1.0VSEL>>

V(C1:2)

0V

250mV

500mV

750mV

Transient response of the monostable multivibrator (detail)

As shown above, the circuit goes back to the initial state after about 2ms.

Page 17: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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Bistable multivibrator This circuit stays in either of two stable states and it alternates between them depending on an external trigger. This circuit is also referred to as flip-flop because it can store 1 bit of information.

R11k

R41k

0

VCC

VCC

0

V1

5Vdc

Q1

Q2N2222

Q2

Q2N2222

R3

10k

R2

10k

Reset

TD = 30ms

TF = 10nsPW = 30msPER = 50ms

V1 = 0.7V

TR = 10ns

V2 = 0V

0

Set

TD = 10ms

TF = 10nsPW = 20msPER = 50ms

V1 = 0.7V

TR = 10ns

V2 = 0V

0

VV

VV

Bistable multivibrator

Time

0s 10ms 20ms 30ms 40ms 50ms 60ms 70ms 80ms 90ms 100msV(R2:2) V(R3:1)

2.5V

5.0V

-1.0VSEL>>

V(Q2:b) V(Q1:b)

0V

250mV

500mV

750mV

Transient response of the bistable multivibrator

Page 18: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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As shown in the simulation, at 0ms, Q1 and Q2 are initially on so the circuit is in an undetermined state. At 10ms a 20ms external trigger called Set brings the base of Q2 down to 0V which turns off Q2 and turns on Q1. At 30ms a 30ms external trigger called Reset brings the base of Q1 down to 0V which turns off Q1 and turns on Q2. The circuit alternates between two states. It is in one state at 10ms-30ms and 60ms-80ms. It is the opposite state at 30ms-60ms and 80ms-100ms.

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Square wave generator This circuit uses positive and negative feedback in order to generate a square wave.

U1

uA741

+3

-2

V+7

V-4

OUT6

OS11

OS25

C1

1u

R1

3k

R2

3k

R31k

0

0

V1 2Vdc V2 2Vdc

0 0

V+ V-

V+

V-

V

Square wave generator

Time

40ms 42ms 44ms 46ms 48ms 50ms 52ms 54ms 56ms 58ms 60msV(R1:2)

-2.0V

0V

2.0V

Transient response of the square wave generator

The oscillating frequency is:

Hz

R

RCR

f 326

12

ln2

1

2

311

The oscillating frequency from the simulation is 343Hz.

Page 20: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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Square/triangle waves generator This circuit generates square and triangular waveforms. U2 integrates the output of U1 and flips it.

C1

1u

R2

1k

R1

1k

R3

1k

0

V1 2Vdc V2 2Vdc

0 0

V+ V-

V+

V-U1

uA741

+3

-2

V+7

V-4

OUT6

OS11

OS25

V-U2

uA741

+3

-2

V+7

V-4

OUT6

OS11

OS25

0V+

V

V

SQUARE

TRIANGLE

Square/triangle waves generator

Time

40ms 42ms 44ms 46ms 48ms 50ms 52ms 54ms 56ms 58ms 60msV(R3:1)

-2.0V

0V

2.0V

SEL>>

V(U1:OUT)-2.0V

0V

2.0V

Transient response of the square/triangle waves generator

The oscillating frequency is:

HzR

R

CRf 250

4

1

3

2

1

The oscillating frequency from the simulation is 255Hz.

Page 21: 501-550 - Oscillatorsice77.net/electronics/Oscillators.pdf · Oscillators are classified as linear or harmonic oscillators if their output is a sinusoidal waveform. 1. Feedback a.

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Triangle/square waves generator This circuit generates square and triangular waveforms. The frequency of the outputs can be modulated by the input voltage so this circuit is a Voltage-Controlled Oscillator (VCO).

U1

uA741

+3

-2

V+7

V-

4

OUT6

OS11

OS25

U2

uA741

+3

-2

V+7

V-

4

OUT6

OS11

OS25

C1

25nF

R1

50k

R3

51k

R4

51k

R2

25k

R5

10k

R6

100k

R7

51k

0

0

0

V1

5Vdc

0

V2

10Vdc

0

V3

10Vdc

0

V+ V-

V+

V+

V-

V-

SQUARE

TRIANGLE

Q1

Q2N2222

V

VV

Triangle/square waves generator

Time

0s 2ms 4ms 6ms 8ms 10ms 12ms 14ms 16ms 18ms 20ms 22ms 24ms 26ms 28ms 30msV(V1:+) V(C1:2) V(U2:OUT)

-10V

-5V

0V

5V

10V

Transient response of the triangle/square waves generator

For this circuit the ratio R1/R2 must be fixed to 1/2. Reducing the value of C1 by half doubles the frequency. Increasing the value of V1 by two also doubles the frequency which confirms this is a VCO. The oscillating frequency from the simulation is about 151Hz. The circuit can be implemented with a MOSFET instead of a BJT.

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555 timer IC The 555 timer IC was designed by Swiss electronics engineer Hans R. Camenzind in 1970 or 1971 and introduced on the market by Signetics in 1971. It is a classical circuit and it can be configured to function just like a multivibrator, an oscillator or a flip-flop with the addition of a few external components such as capacitors and resistors. Internally, the IC can be implemented with BJTs or MOSFETs. Depending on the manufacturer and the implementation, the 555 timer IC has transistors, resistors and diodes. The chip is available in an 8-pin configuration. The 556 version of the timer has 14 pins and it contains 2 555 chips. 558 and 599 versions come in 16-pin chips and they contain 4 modified 555 chips. The NE555 was the first 555 timer IC chip, it was released by Signetics and it was designed for operation between 0°C and +70°C. The SE555 was designed for the military with a temperature range of -55°C to +125°C. A V suffix was used for a plastic package and a T suffix was used for the metal package so that, for example, the SE555T was a military metal packaged 555 timer IC. The 555 timer IC has the following pins:

The chip can be configured to work in the following modes:

Astable or free-running mode Monostable or one-shot mode Bistable or Schmitt-trigger mode

For the following simulations, the TLC555 by Texas Instruments is configured to work in the astable, monostable and bistable modes. Pin 5, the control pin, is always connected to a 10nF capacitor that goes to ground.

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The internal schematic of the BJT implementation of the LM555 timer IC by Texas Instruments

The internal schematic of the CMOS implementation of the TLC555 timer IC by Texas Instruments

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Astable mode

The astable or free-running mode produces an astable multivibrator. For this circuit, the only external components needed are 2 resistors and 2 capacitors.

C1

15n

R1

3.3k

R2

1k

C2

10n

0

0

V1

5Vdc

0

0

Cont

Reset

Vdd

Disch Out

Thresh

Trig

GndU1TLC555

74

1

5

3

8

62

V

The 555 timer IC in astable mode

Time

29.50ms 29.55ms 29.60ms 29.65ms 29.70ms 29.75ms 29.80ms 29.85ms 29.90ms 29.95ms 30.00msV(U1:OUT)

0V

2.0V

4.0V

6.0V

Transient response for the 555 timer IC in astable mode

The oscillating frequency is:

kHzkknFRRC

f 174.18123.3152ln

1

22ln

1

211

The on-time for the pulse is:

skknFRRCton 71.4413.3152ln2ln 211

The off-time for the pulse is:

sknFRCtoff 40.101152ln2ln 21

The oscillating frequency from the simulation is 17.543kHz, the on-time is 46µs and the off-time is 11µs.

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Monostable mode The monostable or one-shot mode produces a monostable multivibrator. For this circuit the only external components needed are 1 resistor and 2 capacitors. Pin 2, the trigger pin, is active low. When the pin is brought low, it will initiate the pulse.

C1

15n

Cont

Reset

Vdd

Disch Out

Thresh

Trig

GndU1TLC555

74

1

5

3

8

62

R1

3.3k

0

C2

10n

0

V1

5Vdc

0

0

V2

TD = 5ms

TF = 1nsPW = 10usPER = 100m

V1 = 5V

TR = 1ns

V2 = 0V

0

V V

V

The 555 timer IC in monostable mode

Time

4.90ms 4.92ms 4.94ms 4.96ms 4.98ms 5.00ms 5.02ms 5.04ms 5.06ms 5.08ms 5.10msV(U1:OUT) V(C1:2)

0V

2.5V

5.0V

SEL>>

V(V2:+)0V

2.5V

5.0V

Transient response for the 555 timer IC in monostable mode The time of the pulse is:

snFkCRt p 38.54153.33ln3ln 11

The pulse ends when the voltage across C1 is 2/3 of the supply voltage.

The time of the pulse from the simulation is 55.1µs.

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29 www.ice77.net

Bistable mode The bistable or Schmitt-trigger mode produces a bistable multivibrator. For this circuit the only external component needed is 1 capacitor. Pin 2, the trigger pin, is active low. When the pin is brought low, it will set the output to a high state. Pin 4, the reset pin, is also active low. When the pin is brought low, it will reset the output to a low state.

0

C1

10n

0

V1

5Vdc

0

0

V3

TD = 7ms

TF = 1nsPW = 100usPER = 100m

V1 = 5V

TR = 1ns

V2 = 0V

0

V2

TD = 4ms

TF = 1nsPW = 100usPER = 100m

V1 = 5V

TR = 1ns

V2 = 0V

0

RESET

SET

Cont

Reset

Vdd

Disch Out

ThreshTrig

GndU1TLC555

64

1

5

3

8

72

V

V

V

The 555 timer IC in bistable mode

Time

3.0ms 3.5ms 4.0ms 4.5ms 5.0ms 5.5ms 6.0ms 6.5ms 7.0ms 7.5ms 8.0msV(U1:OUT)

0V

2.5V

5.0V

V(V3:+)

0V

2.5V

5.0V

V(U1:TRIG)

2.5V

5.0V

SEL>>

Transient response for the 555 timer IC in bistable mode


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