The mid frequency gain of the amplifier circuit shown below with high value of beta of the BJT is
Applying KVL, we get:
Now,
or, this diagram is CE unbypass amplifier so,
In a common source MOSFET amplifier circuit operating at 10 kH z, the drain resistance Rd = 200 kΩ. If MOSFET parameters are gm = 1.5 mA/V, r d = 50 kQ, Cds = 1.0 pF and Cgd = 2.0 pF, the voltage gain is equal to
An npn BJT has g_{m} = 38 mΩ/V, C_{μ} = 10^{14} F, C_{π} = 4 x 10^{13} F and DC current gain, β_{0} = 90. For this transistor f_{T} and f_{β} are respectively
and
G iven for an FET, g_{m} =  9 .5 m A /volt, total capacitance = 500 pF. For a voltage gain of 30, the bandwidth will be
The drain gate capacitance of a junction FET is 2 pF. Assuming a common source voltage gain of 20, what is the input capacitance due to miller effect?
Assertion (A): In the high frequency model of FET, the voltage amplification drops drastically with increase in frequency.
Reason (R): The high frequency model is identical with the low frequency model except that the capacitances between various terminals (gate, source and drain) is added.
The high frequency mode! of FET is shown below.
Because of the internal capacitances (C_{gd}, C_{gs} and C_{ds}), feedback exists between the output and input circuits of the FET in its high frequency model and hence the volta g e amplification drops drastically with the increase in frequency. Moreover, there is no feedback from output to input in the FET small signal (low frequency) model.
Flence, both assertion and reason are correct and reason is the correct explanation of assertion.
For a single stage CE amplifier, g_{m} = 50 mA/V, C_{e}= 1 pF and C_{c} = 0.2 pF. The frequency at which the short circuit commonemitter current gain attains unit magnitude is given by
The frequency at which the short circuit common emitter current gain attains unit magnitude is given by
When the load resistance is zero (short circuit) in a commonemitter configuration, the current flowing from the base to the collector node through the collector capacitor C_{c}, is small because
C_{e} can be as smai as 1 pF, and C_{c} as small as 0.2 pF.
Thus, C_{e }is larger than C_{c}
Consider the following statements:
1. For finding the transistor behaviour at high frequency it is necessary to examine the diffusion mechanism.
2. At low frequency it is assumed that the transistor responds instantly to changes of input voltage or current.
3. The hybridjr model is valid under dynamic conditions when the rate of change of \/BEis small enough so that the base incremental current/^ is small compared with the collector incremental current/^
4. The parameter fTis a frequency characteristic of a transistor.
Which of the above statements are correct?
A modern bipolar transistor can have C_{e} = 1 pF. If g_{m} = 50 mA/V, the f_{T} of a common emitter amplifier will be
or
Use Code STAYHOME200 and get INR 200 additional OFF

Use Coupon Code 







