Transistor As Variable Resistor

- January 04, 2019

In the case of a connection to ground for example an n type mosfet a capacitor a resistor and a pwm will probably suffice for a relatively slow changing pot. Its a magic pot whose knob is mysteriously connected to the diode by invisible rays kind of like this.

Physical Computing At Itp Tutorials Using A Transistor

Electronics Components Amplify With A Transistor Dummies

Transistor Temperature Sensor Circuit

There are two distinct regions.

Transistor as variable resistor. I am looking to design a circuit most likely with a transistor to act as a voltage controlled rheostat. If only two terminals are used one end and the wiper it acts as a variable resistor or rheostat. In the schematic the op posted q2 controls the frequency of a phase shift oscillator.

A potentiometer is a three terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. We have a 2 wire dimmer input to a ballast that presents about 11v unloaded. Yes a transistor is like a variable resistor in that the resistance between collector emitter or drain source is variable.

Its like a valve and either allows current to flow or blocks it from flowing. The circuit should have fairly high input impedance since it will be. The field effect transistor as a voltage controlled resistor we consider the use of a n channel fet as a voltage controlled resistor where the resistance between the drain and source is controlled by the gate source voltage.

The tremolo phase shift oscillator on the lower left modulates the input signal by means of the variable resistance of a transistor driven by the tremolo intensity control. But this isnt just an ordinary pot. Onto these terminals we hook up a simple circuit that basically consists of a npn transistor to collector to emitter and a manual rheostat one end to collector the other to the base which is used very successfully to vary the voltage across these terminals between 1 and 10v.

A transistor within an electronic circuit works like a combination of a diode and a variable resistor also called a potentiometer or pot. The key to designing a solid state variable resistor is operating in your transistor in the active region rather than allowing it to become saturated. The controlling voltage can range from 0 33 v and i am trying to get a resistance range of about 200 5500 ohms.