LT1016 – LS74121 Voltage Controlled Pulse Width Generator/ Monostable Multivibrator

Here’s the Mono-stable multivibrator circuit generates a fixed pulse width when receiving a trigger signal on its input. The pulse width of the output is fixed regardless of the input pulse duration/width. In practical application, the width of the output pulse is determined by choosing the right components values for certain application. In today’s digital electronics, mono-stable function can be easily implemented using micro controller. In many practical they’re more than enough, but many experimental works sometime need very specific function with high speed performance while maintaining its flexibility. This is the figure of the circuit diagram.

High Frequency Generator Circuit

This is a design circuit for high frequency waveform generator is very useful in electronic experiment and design. This circuit is generate sine wave oscillation, but actually we can modify the circuit to generate triangle or square wave function. The core of this waveform generator is MAX038. This integrated circuit chip gives complete function to build a waveform generator/function generator. This is the figure of the circuit;

The frequency can be controlled using current. If we disconnect the 20k RIN from REF (pin 1) and connect it to a DAC, then we can control the frequency using microcontroller or digital interface. We can even control the chip using a quartz crystal (PLL) by controlling the current using a phase comparator output that compares the sync output (pin 14 of MAX038) and a reference clock from quartz crystal oscillator. This waveform generator integrated circuit chip is very interesting since it can generate 0.1Hz to 20MHz, very wide operating frequency, as expected for every waveform generator instruments.

1Hz up to 22MHz Generator Using MAX038

This is a design circuit for simple MAX038 generator. It produces sine, triangle and square waves from 1Hz up to 22MHz. The Amplitude, offset and duty cycle are adjustable to offer wide range of generated signals. This is the figure of the circuit;

Frequency adjustment is made as a rotary switch S8 with a capacitor bank and variable resistor P7. Amplitude, offset and duty-cycle are performed via variable resistors. Switch S5 selects generated waveform. The output at U1-19 is 2V p-p for all waveforms. For amplitude adjustment, P6 and R38 form a voltage divider. The summing amplifier multiplies that voltage, so the signal at the output will vary up tp 24.4V p-p. The offset voltage is controlled by resistor P5. Duty-cycle adjustment is controlled by resistor P4.

555 Ramp Generator Circuit

This is a design circuit that can using a 555 timer IC as an astable multi vibrator, or oscillator. This time, however, we will compare its operation in two different capacitor-charging modes: traditional RC and constant-current. This is the figure of the circuit;

Connecting test point #1 (TP1) to test point #3 (TP3) using a jumper wire. This allows the capacitor to charge through a 47 kΩ resistor. When the capacitor has reached 2/3 supply voltage, the 555 timer switches to "discharge" mode and discharges the capacitor to a level of 1/3 supply voltage almost immediately. The charging cycle begins again at this point. Measure voltage directly across the capacitor with a voltmeter (a digital voltmeter is preferred), and note the rate of capacitor charging over time. It should rise quickly at first, then taper off as it builds up to 2/3 supply voltage, just as you would expect from an RC charging circuit.

Remove the jumper wire from TP3, and re-connect it to TP2. This allows the capacitor to be charged through the controlled-current leg of a current mirror circuit formed by the two PNP transistors. Measure voltage directly across the capacitor again, noting the difference in charging rate over time as compared to the last circuit configuration.

Cuckoo Sound Simulator (Synthesizer/Generator) Circuit

A two tone effect very much alike cuckoo sound is generated by this circuit. We can use this circuit for door-bells or other purposes thanks to a built-in audio amplifier and loudspeaker. Used as a sound effect generator, it can be connected to external amplifier, tape recorder, etc. The built-in audio amplifier and loudspeaker may be omitted and the output taken from C8 and ground in this case. There are two options: when SW1 is left open, we can use free running and when SW1 is closed we can use one-shot. A two-tone cuckoo sound will be generated each time P1 pushbutton is pressed in this case. This is the figure of the circuit;

IC1 is wired as a squarewave generator and two tones of cuckoo sound is produced by this IC. The frequency of the higher one (667Hz) is set by means of Trimmer R2. A further trimmer (R22) is added to IC1 timing components via D6, and the lower tone (545Hz) is generated when IC2D output goes low. The the squarewave output of IC1 is converted to a quasi-sinusoidal waveform by R3, R4, C3 and C4, then mixed with the white noise generated by Q1, R6 to imitate closely the cuckoo sound.Q2 has two purposes: it mixes the two incoming signals and gates the resulting tone, shaping its attack and decay behavior by means of the parts wired around its Emitter.

R15 is the volume control and IC4 is the audio power amplifier driving the speaker. The clock generator IC2A driving the decade counter IC3 provides the various sound and pause timings for the circuit. Some output pins of this IC are gated by IC2C, IC2D and related components to drive appropriately the sound generator and the sound gate. The circuit operates in the free-running mode and a cuckoo sound is generated continuously when SW1 is left open. the circuit generates two tones then stops, because a high state appears at the last output pin (#11) of the decade counter IC: therefore the count is inhibited by means of D1 feeding pin #13 when SW1 is closed. When P1 is pressed, the circuit is reset by a positive pulse at pin #15 of IC3. If the two tones frequencies are set precisely, the best result will be obtained. i.e. 667Hz for the first tone and 545Hz for the second (called Minor Third in musical terms). If available, a digital frequency would be the best tool to set up R2 and R22. You can use a musical instrument such as piano or guitar. Here’s the step to tuning-up the notes by musical instrument: First, we have to disconnect R22 from D6 diode temporarily then connect the digital frequency counter to pin 3 od IC1. To read 667Hz on the display, adjust R2 in order then connect R22 to negative ground and adjust it to read 545 Hz on the display and finally reconnect R22-D6.

Then, steps to tuning by ear: First, disconnect R22 from D6 anode temporarily. Disconnect C8 from Q2 Collector and connect it to R4, C4 and C5 junction. After that, adjust R2 in order that the tone generated by the loudspeaker is at the same pitch of the reference note generated by your musical instrument. This reference note will be the E written on the stave in the fourth space when using the treble clef. Then, Connect R22 to negative ground and adjust it in order that the tone generated by the loudspeaker is at the same pitch of the reference note generated by your musical instrument. This second reference note will be the C-sharp written on the stave in the third space when using the treble clef. Finally reconnect R22-D6 and C8-Q2 connections. For your note, the master clock can be adjusted by means of R18. The percentage of hiss and sound in the mixing circuit, setting the tone character, can be varied changing R8 and R7 values respectively. Any kind of dc voltage supply in the 12 – 15V range can be used, but please note that supply voltages below 12V will prevent operation of the white noise generator and an amusing application of this circuit is to use a photo-resistor in place of P1, then placing the unit near the flashing lamps of your Christmas tree. A sweet cuckoo sound will be heard each time the lamp chosen will illuminate.

Astable Circuit Produce Pulses Using 555 Timer IC

This is circuit that first introduced by Signetics Corporation as the SE555/NE555 about 1971. Pin connections and functions: (See schematic below for basic circuits). Pin 1 (Ground) – The ground (or common) pin is the most-negative supply potential of the device, which is normally connected to circuit common when operated from positive supply voltages.  Pin 2 (Trigger) – This pin is the input which causes the output to go high and begin the timing cycle. Triggering occurs when the trigger input moves from a voltage above 2/3 of the supply voltage to a voltage below 1/3 of the supply. This is the figure of the circuit.

For example using a 12 volt supply, the trigger input voltage must start from above 8 volts and move down to a voltage below 4 volts to begin the timing cycle. The action is level sensitive and the trigger voltage may move very slowly. To avoid retriggering, the trigger voltage must return to a voltage above 1/3 of the supply before the end of the timing cycle in the mono stable mode. Trigger input current is about 0.5 micro amps. Pin 3 (Output) – The output pin of the 555 moves to a high level of 1.7 volts less than the supply voltage when the timing cycle begins. The output returns to a low level near 0 at the end of the cycle. Maximum current from the output at either low or high levels is approximately 200 mA. Pin 4 (Reset): – A low logic level on this pin resets the timer and returns the output to a low state. It is normally connected to the + supply line if not used.

Pin 5 (Control) – This pin allows changing the triggering and threshold voltages by applying an external voltage. When the timer is operating in the astable or oscillating mode, this input could be used to alter or frequency modulate the output. If not in use, it is recommended installing a small capacitor from pin 5 to ground to avoid possible false or erratic triggering from noise effects. Pin 6 (Threshold) – Pin 6 is used to reset the latch and cause the output to go low. Reset occurs when the voltage on this pin moves from a voltage below 1/3 of the supply to a voltage above 2/3 of the supply. The action is level sensitive and can move slowly similar to the trigger voltage. Pin 7 (Discharge) – This pin is an open collector output which is in phase with the main output on pin 3 and has similar current sinking capability. Pin 8 (V +) – This is the positive supply voltage terminal of the 555 timer IC. Supply-voltage operating range is +4.5 volts (minimum) to +16 volts (maximum).

High Frequency Waveform Generator

This is the circuit of waveform generator. Waveform generator is very useful in electronic experiment and design. This circuit is generates sine wave oscillation, but actually we can modify the circuit to generate triangle or square wave function. This is the figure of the circuit.


This circuit is based on MAXIM IC. This integrated circuit chip gives complete function to build a waveform generator/function generator. Here some of modifications that can be used to build a complete waveform generator circuit:

· The circuit can be used to generate square wave, triangle, or sine wave by programming the pin inputs (A0: pin 3, A1:pin 4).
o A0 A1 WAVEFORM
o X 1 Sine wave
o 0 0 Square wave
o 1 0 Triangle wave

· The frequency can be controlled using current. If we disconnect the 20k RIN from REF (pin 1) and connect it to a DAC, then we can control the frequency using microcontroller or digital interface. We can even control the chip using a quartz crystal (PLL) by controlling the current using a phase comparator output that compares the sync output (pin 14 of MAX038) and a reference clock from quartz crystal oscillator.