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Special-Purpose Op-Amp Circuits - Technical MCQs

Q1:

The voltage gain of an OTA can be calculated using the formula

A mca20_1002a1.gif

B mca20_1002b1.gif

C mca20_1002c1.gif

D mca20_1002d1.gif

ANS:B - mca20_1002b1.gif

A transconductance amplifier basically computes a tanhyperbolic.
It operates linearly for a very small range of inputs and smoothly transits to saturation.
Gm = Ic/2 Vt.
Then the voltage gain Av is
Av = gm.Rl =Ic.Rl/2Vt

Thus the voltage gain of the OTA CKT can be externally controlled by the control current Ic.