Unit 4 - Operational Amplifiers

About

High-gain differential amps

10-10^5 gain

Feedback system

Performance parameters

Gain

Precision of feedback system

Trade-off of gain vs speed and o/p voltage

Know minimum value

Exercises

Nominal Gain Beta

Gain error = (Beta-Av)/Beta

Small-signal BW

Frequency increase, gain decrease

Gain x BW= unity-gain frequency (fu)

Large errors

Output swing

Large

fully-diff op-amps

complementary o/p

doubles swing

Trades with speed

Linearity

Non-linear

differential Id and Vin nonlinear

Distorted O/P

Harmonics

Noise

Minimum signal level

Large dimensions

Bias currents

Trades with Output swing

Connected to noisy supply lines

Supply rejection

noisy input

Fully differential topologies

One-Stage Op-amps

Basic Topologies

Diff I/P, single ended O/P image

Diff I/P, differential O/P image

Characteristics

Small-signal, low freq gain

gmn(r0n||r0p) ≤ 10 in nm

BW decided by Load Capacitance

Noise - All transistors