Transimpedance Amplifiers

A transimpedance amplifier (TIA) is a current to voltage converter which is used to amplify the current output from different types of sensors to a proportional voltage. Transimpedance amplifiers are used with sensors which have a current response that is more linear than the voltage response.

Transimpedance amplifiers are also referred to as current to voltage converters or I to V converters.

Passive or Active?

• Passive current to voltage converters uses only passive elements. There are however limitations with these types of amplifiers as the current source and output load must be ideal for proper operation. The output load resistance must be close to infinity, current from the current source must be independent of the voltage and the current source must have infinite internal resistance. As these conditions are virtually impossible to attain, passive current to voltage converters is rarely used.
• Active current to voltage converters is based on active elements like a bipolar junction transistor (BJT), field-effect transistor (FET) or an operational amplifier (opamp). The most common combination is using a transimpedance amplifier with an operational amplifier.

What are the typical applications of the transimpedance amplifier?

There are a lot of possible applications for transimpedance amplifiers due to the amount of day to day electronics we use. A transimpedance amplifier allows for more advanced circuitry such as servomechanisms and light meters.

What is the accuracy of a transimpedance amplifier?

The accuracy may depend on many aspects of the signal such as its condition, hysteresis or linearity. Also, the working temperature and environmental conditions have an impact on accuracy. This can be improved by using additional circuit integrated elements e.g. noise filters.

What are the most important specifications of TIA?

Before making a decision os one TIA or another, you should consider a few most important values e.g:

• Bandwidth
• Noise
• Signal bandwidth
• Gain
• Capacitance