An astable circuit is a type of electronic circuit that does not have a stable output state. This means that the output will continuously switch between two states, typically high and low, at a predetermined frequency.
An Op Amp, or operational amplifier, is a type of electronic component that is commonly used in circuit design. It is a high-gain, direct-coupled amplifier that can be used to amplify, filter, or perform mathematical operations on analog signals.
In order to control TH, TL, VH, and VL in an astable circuit with an Op Amp, you will need to use a combination of resistors and capacitors in the circuit design. The values of these components will determine the frequency and duty cycle of the output signal, which in turn will control the high and low thresholds (TH and TL) and the high and low voltage levels (VH and VL).
While there are many different types of Op Amps available, not all of them are suitable for designing an astable circuit. It is important to choose an Op Amp with a high slew rate and a wide frequency response in order to achieve the desired output frequency and duty cycle.
Astable circuits with Op Amps are commonly used in electronic devices such as clocks, timers, and pulse generators. They can also be used in communication systems, audio equipment, and other electronic devices that require a stable and adjustable frequency signal.