S S KIRAN: Voltage to Current Converter

Voltage to Current Converter

A voltage to current converter is used for low voltage DC and AC voltmeter, LED and Zener Diode Tester. Voltage to Current Converter is used in Voltmeters hence here we can observe device and its internal board.

Voltage to Current Converter is also used for Zener Diode Test

Simple Voltage to Current Converter

When we confer about the connection between voltage and current, it is obvious to mention the Ohm’s law.

Voltage to Current Converter Using Op-Amp

Op-amp is implemented to simply convert the voltage signal to corresponding current signal. The Op-amp used for this purpose is IC LM741. This Op-amp is designed to hold the precise amount of current by applying the voltage which is essential to sustain that current through out the circuit. They are of two types that are explained in detail below.

Types:

a. Floating Load Voltage to Current Converter

b. Ground Load Voltage to Current Converter

Floating Load Voltage to Current Converter

As the name indicates, the load resistor is floating in this converter circuit. That is, the resistor R_L is not linked to ground. The voltage, V_IN which is the input voltage is given to the non-inverting input terminal. The inverting input terminal is driven by the feedback voltage which is across the R_L resistor. This feedback voltage is determined by the load current and it is in series with the V_D, which is the input difference voltage. So this circuit is also known as current series negative feedback amplifier.

For the input loop, the voltage equation is

Since A is very large,

Since, the input to the Op-amp

From the above equation, it is clear that the load current depends on the input voltage and the input resistance. That is, the load current, , which is the input voltage. The load current is controlled by the resistor, R. Here, the proportionality constant is 1/R. So, this converter circuit is also known as Trans-Conductance Amplifier. Other name of this circuit is Voltage Controlled Current Source. The type of load may be resistive, capacitive or non-linear load. The type of load has no role in the above equation. When the load connected is capacitor then it will get charge or discharge at a steady rate. Due to this reason, the converter circuit is used for the production of saw tooth and triangular wave forms.

Ground Load Voltage to Current Converter

This converter is also known as Howland Current Converter. Here, one end of the load is always grounded. For the circuit analysis, we have to first determine the voltage, V_IN and then the relationship or the connection between the input voltage and load current can be achieved.