# V to I and I to V Converters

## Voltage to Current Converter

• Voltage to current converter produce a current which is directly proportional to the applied voltage and the resistance used in the circuit. It should be noted that all the resistances used in the circuit are equal to R. Voltage to Current converter

## Voltage to Current Converter with floating loads (V/I) :

• Voltage to current converter in which load resistor RL is floating (not connected to ground).
• Vin is applied to the non-inverting input terminal, and the feedback voltage across R1 devices the inverting input terminal.
• This circuit is also called as a current – series negative feedback amplifier. Because the feedback voltage across R1 (applied Non-inverting terminal) depends on the output current i0 and is in series with the input difference voltage Vid. Writing KVL for the input loop,
Voltage Vid=Vf and IB=0, Vi = RLi0 Where io=Vi/RL

Input voltage Vin is converted into output current of Vin/RL [Vin -> i0].
In other words, input volt appears across R1. If RL is a precision resistor, the output current (i0 = Vin/R1) will be precisely fixed.

## Applications

• Low voltage ac and dc voltmeters
• Diode match finders
• LED and Zener diode testers

## Voltage to current converter with Grounded load :

• This is the other type V – I converter, in which one terminal of the load is connected to ground. • For the circuit analysis , we have to first determine the voltage , VIN and then the relationship or the connection between the input voltage and load current can be achieved.

For that, we apply Kirchhoff’s current law at the node V1 For a non-inverting amplifier, gain is A = 1 + ( RF / R1 )
Here, the resistor, RF = R = R1.
So, A = 1 + R/R = 2.

Hence the voltage in the output will be Thus, we can conclude from the above equation that the current IL is related to the voltage, VIN and the resistor, R.

## Current to Voltage Converter

• A current to voltage converter will produce a voltage proportional to the given current. This circuit is required if your measuring instrument is capable only of measuring voltages and you need to measure the current output. Current to Voltage converter

Open – loop gain A of the op-amp is very large. Input impedance of the op amp is very high.

## Sensitivity of the I – V converter :

• The output voltage V0 = -RFIin.
• Hence the gain of this converter is equal to -RF. The magnitude of the gain (i.e) is also called as sensitivity of I to V converter.
• The amount of change in output volt ∆V0 for a given change in the input current ∆Iin is decide by the sensitivity of I-V converter.
• By keeping RF variable, it is possible to vary the sensitivity as per the requirements.

## Applications of I – V converter :

• One of the most common use of the current to voltage converter is
• Digital to analog Converter (DAC)
• Sensing current through Photodetector such as photocell, photodiodes and photovoltaic cells.
• Photoconductive devices produce a current that is proportional to an incident energy or light (i.e) It can be used to detect the light.