Next: Open Loop Analysis
Up: Differential Amplifiers and Op-Amp
Previous: Experiment
The circuit in Fig. (5.5) represents a very simple op-amp.
It is virtually the same circuit as in the previous section,
except there is an emitter follower
stage and feedback added.
In the circuit, the input signal is applied to Q1.
Since the output of the diff-amp is taken from the collector of Q2, the base
of Q1 represents
the noninverting input.
The output of Q2 is then input to Q4 which is forms a directly coupled
emitter follower stage. The purpose of Q4 is to reduce the output
resistance of the circuit.
When feedback is applied,
a fraction of the output voltage is then
fed back to the inverting input (Q2).
This provides negative feedback by in effect, reducing the
total voltage between the bases of Q1 and Q2.
Figure 5.5:
Simple Op-Amp-Like Circuit
|
Neil Goldsman
10/23/1998