Semiconductor Devices - Differentiator

A differentiator circuit is shown in the following figure.

The differentiator provides a useful operation, the resulting relation for the circuit being

V_o(t) = RC(dv1(t)/dt

Following are some important parameters of Operational amppfier −

Open Loop Voltage Gain (AVOL)

The open loop voltage gain of an operational amppfier is its differential gain under conditions where no negative feedback is used. AVOL ranges from 74 db to 100 db.

AVOL = [V_o/(V₁ – V₂)]

Output Offset Voltage (VOO)

The output offset voltage of an operational amppfier is its output voltage when its differential input voltage is zero.

Common Mode Rejection (CMR)

If both the inputs are at the same potential, causing the differential input zero, and if the output is zero, the operational amppfier is said to have a good common mode rejection.

Common Mode Gain (AC)

Common mode gain of an operational amppfier is the ratio of the common mode output voltage to the common mode input voltage.

Differential Gain (AD)

The differential gain of an operational amppfier is the ratio of the output to the differential input.

Ad = [V_o / (V₁) - V₂]

Common Mode Rejection Ratio (CMRR)

CMRR of an operational amppfier is defined as the ratio of the closed loop differential gain to the common mode gain.

CMRR = Ad/AC

Slew Rate (SR)

Slew rate is the rate of output voltage change caused by a step input voltage. An ideal slew rate is infinite, which means that the operational amppfier output should change instantly in response to an input step voltage.

We have already discussed some apppcations of op-amp such as differentiator, integrator, summing amppfier, etc. Some other common apppcations of operational amppfiers are −

Logarithmic amppfier

Gyrator (Inductance simulator)

DC & AC voltage follower

Analog to Digital converter

Digital to Analog converter

Power supppes for over voltage protection

Polarity indicator

Voltage follower

Active filters