What is transconductance amplifier used for?
The Operational Transconductance Amplifier, or OTA as it is normally abbreviated, is primarily used as a controlled-gain block. This means that an external controlling signal, either a current or a voltage, will be used to set a key parameter of the circuit, such as closed-loop gain or f2.
Why current series amplifier is a transconductance amplifier?
Current series feedback amplifier is also called as series fed amplifier or transconductance amplifier. When the part of the output current is sampled and given to the feedback circuit, where the fraction of current is converted into a proportional voltage and then given as input signal.
How is the transconductance of an amplifier determined?
The voltage gain is then the output voltage divided by the differential input voltage: The transconductance of the amplifier is usually controlled by an input current, denoted I abc (“amplifier bias current”). The amplifier’s transconductance is directly proportional to this current.
How are the anodes of a transconductance amplifier biased?
As depicted in the diagram, the anodes of the diodes are attached together and the cathode of one is attached to the non inverting input (Vin+) and the cathode of the other to the inverting input (Vin−). The diodes are biased at the anodes by a current (I bias) that is injected into the I bias terminal.
What is the value of transconductance in a MOSFET?
Similarly, in field effect transistors, and MOSFETs in particular, transconductance is the change in the drain current divided by the small change in the gate/source voltage with a constant drain/source voltage. Typical values of g m for a small-signal field effect transistor are 1 to 30 millisiemens.
How is the output current of an OTA calculated?
In the ideal OTA, the output current is a linear function of the differential input voltage, calculated as follows: where V in+ is the voltage at the non-inverting input, V in− is the voltage at the inverting input and g m is the transconductance of the amplifier.