A stepped voltage generator is an electronic circuit designed to generate a sequentially stepped voltage waveform, which resembles a sinusoidal appearance, but has a stepped voltage pattern ascending sequentially upwards towards the peak and then descending sequentially downward with identical steps towards the 0V line to complete a cycle of the waveform.
How the Circuit Works
The figure below exhibits a useful application of the IC 4066 quad bilateral switch. In this circuit, the 4066 (U1) is configured to carry out sequential switching, in order to generate a uniform stepped waveform; as indicated in the next figure. As demonstrated, the generator's waveform consists of 3-up and 3- down steps through 1V increments.
The triggering for the 4066 internal switches is governed by a 4017 decade counter/divider (U2); a 567 tone decoder set up like a squarewave generator provides the required clock pulses for the IC 4017.
The 4017 is rigged to count from 0 to 5 (0-1-2-3-4-5) sequentially and reset on the rising edge of the seventh step by coupling pin 5 (output 6) of U2 to pin 15 (reset).
As soon as output 6 (pin 5 of U2) becomes high, the reset terminal of U2 pushes output 0 (pin 3) to flip from low to high, starting the pattern afresh.
The high pin-3 output (output 0) of U2 is given to the control pin of the 1st U1 switch, switching it on and consequently connecting the intersection of R4 and R5 with the output bus.
This sets up step one with a one-volt level. With the following clock pulse from the 567, the 4017 generates a high output at pin 2, which is applied via D4 to another switch control at pin 5, switching it on.
This links the R3, R4 with the output bus. The 2nd step constitutes a 2-volt output. For the subsequent pulse obtained via U3, pin 4 of U2 turns high, evoking the 3rd switch (in U1) to activate, which respond to generate a 3- volt output intended for step 3.
The 4th pulse coming from U3 results in pin 7 to become high, switching on the very last switch, and thus creating a 4-volt output for step 4.
The fifth pulse feeds a high to pin 10 of U2, which moves by means of D4 to the control input of the 3rd switch, switching it on (for a second occasion) and providing a 3-volt output to the 5th step.
For the subsequent clock pulses, the switch attached to pin 6 of U1 is yet again activated, generating a 2-volt output for step 6. Soon after step six is accomplished, the counter resets and commences back from the start by switching on the 1st switch for step 1.
Each waveform step can be arranged for any voltage right from zero to 100 % supply voltage through the use of specific voltage dividers for each step. Additionally, the generator's output could be buffered to deliver adequate voltage and current outputs to provide rising voltage or current supply for a semiconductor curve tracer.
Another Simple Stepped Voltage Generator Circuit
The next design below is even simpler to build as it employs just a couple ICs for the required stepped waveform creation.
However, the design is implemented in a manual mode, wherein the sequential steps of the waveform are developed by tapping the push button S1 at a specific timed rate. Each pressing causes the output of the IC 4017 to shift from pin3 upwards, towards pin11.
In the process, the common ends of the resistors happen to develop a sequentially ascending and descending stepped voltage due to the effect of the varying potential divider formed by the interaction of the shifting IC 4017 logics across the resistors R2---R10 and the ground resistor R13.
Since the common joined ends of the resistors are together fed to the base of a common-emitter BJT stage, the stepped voltage is replicated at the emitter of the 2N2222 transistor with a higher current level, which can be integrated with any suitable external circuit stage for a desired execution.
The manually controlled switch can be replaced with an automatic oscillator stage as indicated in the following example, which shows the implementation of the above stepped voltage generator in a police lamp effect simulator circuit.
Applications
You will find a variety of applications for this circuit. The stepping waveform generator could be implemented to produce numerous progressive voltages for examining the on/off switching point of many CMOS units. It can be effectively used for making efficient sine wave inverters and converters.
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