Voltage Controlled Resistor Circuit

Vcos are used in fm modulation mainly.

Voltage controlled resistor circuit. 4 8 a shown conceptually in fig. One side of the load resistance is connected directly to ground. In this case it used to make a two tone siren which you can see in operation in the video below. A voltage controlled resistor is a three terminal active device with one input port and two output ports.

In the ohmic region1 the drain to source current i. Floating vcrs can be placed between two passive or active components. When a voltage controls the frequency of an oscillator it is called a voltage controlled oscillator or vco for short. Here s a subcircuit for this device subckt vc res1 10k 1 2 4 5 eres 1 3 value i vsense 10k v 4 5 vsense 3 2 dc 0v ends.

This type of circuit is commonly used in electronics to drive current controlled devices like bjt scr etc. As one example the circuit in fig. The basic circuit forms a voltage divider as shown in figures 3 4 5 and 6. Grounded vcrs the more common and les.

Basic voltage controlled resistor vcr circuits one of the simplest uses of a voltage controlled resistor is an electronically controlled attenuator or volume control. All you need is a controlling voltage to multiply the resistor value. 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 input port voltage controls the value of the resistor between the output ports.

In addition to the other fine ideas you could use a voltage controlled oscillator to produce a clock of variable frequency and then use switched capacitor techniques to produce an effective resistor that varies with clock frequency. Vcrs are most often built with field effect transistors. A voltage controlled resistor can be used to change the frequency of an oscillator. 4 8 b represents a voltage controlled attenuator in which the voltage transfer through the circuit can be varied electronically.

It is ground referenced. The jfet and the mosfet. There are two distinct regions. V i x r x vc.

In a voltage controlled current source circuit as the name implies a small amount of voltage across the input will proportionally control the current flow across the output loads. The voltage gain is easily found by voltage division to be v o v s r on r on r 1 1 r r on 1 1 k n r v gg v tn 4 17 by adjusting the value of v. Two types of fets are often used.