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 सोमवार, 6 मई 2019 Biasing Circuits
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
सोमवार, 6 मई 2019 Biasing Circuits
Is this Q-point suitable ? सोमवार, 6 मई 2019 Biasing Circuits
Emitter-Feedback Circuit सोमवार, 6 मई 2019 Biasing Circuits
Stability provided by Negative Feedback सोमवार, 6 मई 2019 Biasing Circuits
Analysis For Input Section : For Input Section : सोमवार, 6 मई 2019 Biasing Circuits
From the output section : सोमवार, 6 मई 2019 Biasing Circuits
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
सोमवार, 6 मई 2019 Biasing Circuits
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
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 सोमवार, 6 मई 2019 Biasing Circuits
सोमवार, 6 मई 2019 Biasing Circuits
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 5 %. That is, सोमवार, 6 मई 2019 Biasing Circuits
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
सोमवार, 6 मई 2019 Biasing Circuits
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
सोमवार, 6 मई 2019 Biasing Circuits
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
सोमवार, 6 मई 2019 Biasing Circuits
सोमवार, 6 मई 2019 Biasing Circuits
सोमवार, 6 मई 2019 Biasing Circuits
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
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
सोमवार, 6 मई 2019 Biasing Circuits
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