Voltage Controlled Resistor Ic

A voltage controlled resistor vcr is a three terminal active device with one input port and two output ports.

Voltage controlled resistor ic. The basic circuit. Two types of fets are often used. Avoltage controlled attenuator as one example the circuit in fig. The circuit is shown in figure 7 and allows the gate control voltage to be the same value as that voltage used without a feedback circuit while preserving.

1 where vin is the differential input voltage kt q is approximately 26 mv at 25 c and i5 and i4 are the collector. The jfet and the mosfet there are both floating voltage controlled resistors and grounded floating. Circuit vc resistor1 cir download the spice file. This type of circuit is commonly used in electronics to drive current controlled devices like bjt scr etc.

Basic voltage controlled resistor vcr circuits. The input port voltage controls the value of the resistor between the output ports. Vcrs are most often built with field effect transistors fets. Use of a floating supply be tween the resistor junction and the fet gate will over come this problem.

4 8 b represents a voltage controlled attenuator in which the voltage transfer through the circuit can be varied electronically. D continuous voltage controlled resistance d high off isolation d high input impedance. D gain ranging capability wide range signal attenuation d no circuit interaction d simplified drive. 7 3 1 circuit description the differential transistor pair q4 and q5 form a transconductance stage in that the ratio of their collector currents is defined by the differential input voltage according to the transfer function.

4 8 a shown conceptually in fig. The answer is yes e g vcr11 but it turns out that virtually any other fet e g jfet and mosfet can be used as a voltage controlled resistor. One of the simplest uses of a voltage controlled resistor is an electronically controlled attenuator or volume control. A common request from spice users is a voltage controlled resistor.

Although there s no spice component that directly models this device you can easily put one together. From the fact that the control signal is well isolated from the resistor terminals. Vcr4n jfet voltage controlled resistor.