Voltage to current converter (V-I converter)
This circuit is one of the simplest voltage to current converters
to drive low loads. In this example a small 0,25 Watts speaker,
with 8Ù resistance, is driven. It is suitable for
microcontroller designs or any other circuit that uses PWM (TTL
logic). You can use it for analog signals as well.
The circuit is not amplifying the input voltage signal
(use a preamp if it is necessary). For analog signals is
better to use a power supply higher than the maximum voltage of
the input signal, to avoid saturation effects. For digital
signals it is not necessary.
The equation applied to this
circuit is I = Vin/R (where R is
22 Ohms, and I the current at the transistor's emitter).
- One 22 Ohm resistor (1/2 Watt).
- One BC 337 transistor.
- One LM358 OPAMP .
- One speaker (0.25 Watt, 8Ù Resistance).
- A 8 pin DIP socket (for the LM358 chip).
- A small piece of a Veroboard
- Wire for connections
- Solder and soldering iron
Also you will need a stabilized 5 Volt external power supply.
You can use a 4.5 Volt battery or even a 9Volt battery. Higher
voltages can also be used (e.g. 12 Volts).