Thought of the Day Best Engineers and Designers use a Process,

Thought of the Day Best Engineers and Designers use a Process,
rather than a formula. Formulae are hard to remember, and often they apply only to one particular situation. सोमवार, 6 मई 2019 Biasing Circuits

Biasing Circuits D.C. Kulshreshtha सोमवार, 6 मई 2019 Biasing Circuits

Collector-to-Base Bias Circuit
सोमवार, 6 मई 2019 Biasing Circuits

Stability provided by Negative Feedback

It reduces the shift in Q-point.
Negative feedback exists when an increase in an output quantity produces a decrease in an input quantity. It reduces the shift in Q-point. सोमवार, 6 मई 2019 Biasing Circuits

Analysis For input Loop : Now, IC = β IB, सोमवार, 6 मई 2019
Biasing Circuits

Is this Q-point suitable ?

Emitter-Feedback Circuit

Stability provided by Negative Feedback

Analysis For Input Section : For Input Section : सोमवार, 6 मई 2019
Biasing Circuits

From the output section :

Drawbacks of the Circuit
The resistor RE also provides ac signal feedback. This can be overcome by using a bypass capacitor CE . For effective bypass, we must have सोमवार, 6 मई 2019 Biasing Circuits

Second is the drawback in the design. Consider,
To make IC independent to β, we must have सोमवार, 6 मई 2019 Biasing Circuits

There are two ways of doing it :
Make RE high. Requires high VCC. Make RB low. Requires low VBB. Hence, this circuit is seldom used. सोमवार, 6 मई 2019 Biasing Circuits

New Design is needed We make a little change in the fixed bias circuit. The Q-point becomes rock-solid. सोमवार, 6 मई 2019 Biasing Circuits

Why is the Emitter-Bias Circuit Immune to Changes in β ?
The reason lies in the process used : In this process, have we used β anywhere ? It sets up a fixed emitter current. सोमवार, 6 मई 2019 Biasing Circuits

Voltage-Divider Bias Circuit

Approximate Analysis सोमवार, 6 मई 2019 Biasing Circuits

This calculation is valid only if base current is small. How small ?
Design rule is that it should be 20 times smaller. This ensures that the error is less than %. That is, सोमवार, 6 मई 2019 Biasing Circuits

Checking the assumption :
The worst case is the lowest current gain, for which This value too is less than critical value of 41 μA. Note that in determining IC nowhere we have used β0. Hence, Q-point is independent of β0 सोमवार, 6 मई 2019 Biasing Circuits

Checking of assumption :
Actual Base Current, सोमवार, 6 मई 2019 Biasing Circuits

More Accurate Analysis
We use Thevenin’s theorem. We thevenize the network on the left of terminals AB सोमवार, 6 मई 2019 Biasing Circuits

Note that we have made no approximations.
Let us now see how much difference it makes to follow the exact analysis. सोमवार, 6 मई 2019 Biasing Circuits

Biasing the FET Here, we need reverse-biasing of the input junction.
Hence, biasing is much simpler. Bias stabilization is also much simpler. Self-bias circuit is normally used. सोमवार, 6 मई 2019 Biasing Circuits

Bias Stabilization Effect of temperature rise :
The mobility of current carriers decreases. Hence, ID decreases. Depletion region decrease. Hence, ID increases. सोमवार, 6 मई 2019 Biasing Circuits

Review Collector-to-Base Bias Circuit. Emitter-Feedback Circuit.
Drawbacks of the Circuit. New Design is needed. Voltage-Divider Bias Circuit. Approximate Analysis. More Accurate Analysis. Biasing the FET. सोमवार, 6 मई 2019 Biasing Circuits

Thought of the Day Best Engineers and Designers use a Process,

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Thought of the Day Best Engineers and Designers use a Process,

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विषय पर प्रस्तुति: "Thought of the Day Best Engineers and Designers use a Process,"— प्रस्तुति प्रतिलेख:

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