Introduction to Transistors
- What is the structure of a junction field effect transistor and how is it different from a BJT? In one line A JFET is a bar of n-type (or p-type) semiconductor forming a channel between source and drain, with heavily doped regions of th... 1
- What is the structure of a bipolar junction transistor and why are its three regions doped differently? In one line A BJT is a three-layer semiconductor device (n-p-n or p-n-p) with an emitter, a base and a collector forming two p-n junctions;... 1
- How does an NPN transistor work in the active region, and what are alpha and beta? In one line In the active region, the forward-biased emitter-base junction injects electrons into the thin base, almost all of which are swe... 1
- What are the input and output characteristics of a BJT in common emitter configuration? In one line In common emitter (CE) configuration, the input characteristic is I_B versus V_BE at constant V_CE , and the output characterist... 1
- How does an n-channel JFET operate, and what are pinch-off and its drain characteristics? In one line In an n-channel JFET, a negative gate-source voltage widens the depletion regions and narrows the channel, reducing drain curren... 1
- How is an enhancement MOSFET built, and how does a gate voltage create a conducting channel? In one line An enhancement n-channel MOSFET has n^+ source and drain regions in a p-type substrate and a metal gate insulated by a thin oxid... 1
- How does a common emitter BJT amplifier amplify a small signal, and why is output inverted? In one line A CE amplifier is biased at a Q-point in the active region; a small AC input at the base varies the base current, which varies t... 1
- How does a FET work as an amplifier in the common source configuration? In one line In a common-source FET amplifier, the FET is biased in its saturation (pinch-off) region; a small AC gate voltage varies the dra... 1
- How do BJTs and MOSFETs work as electronic switches between cut-off and saturation? In one line A transistor works as a switch by being driven fully OFF (cut-off, like an open switch) or fully ON (saturation for a BJT, low-r... 1
- How are transistors used in oscillators, and what is the Barkhausen criterion for oscillation? In one line An oscillator is an amplifier (BJT or FET) with positive feedback through a frequency-selective network; it produces a sustained... 1
- Differentiate between BJT and FET. PointBJTFET (JFET/MOSFET) CarriersBipolar: both electrons and holesUnipolar: only majority carriers ControlCurrent-controlled device (I_C =... 1
- With the help of a neat circuit diagram explain the operation of a BJT as a switch. +Vcc | Rc LOAD (lamp/relay/LED) | +-----o Vout = V_CE | Vin o-RB--| B NPN (CE) | E | GND An NPN transistor in common-emitter configuration i... 1
- Explain CE configuration of BJT with the input and output characteristics. Common-emitter (CE) configuration: emitter is common to input and output. Input is applied between base and emitter (V_BE, I_B); output is t... 1
- Compare BJT and FET PointBJTFET (JFET/MOSFET) CarriersBipolar: both electrons and holesUnipolar: only majority carriers ControlCurrent-controlled device (I_C =... 1
- Explain the application of BJT as an amplifier. BJT as an amplifier (common-emitter, NPN, voltage-divider bias): +Vcc R1 | Rc | +--/\/\/--+------||-----o Vout Vin o--||-+---- B C | Cc2 (to... 1
- Write a short note on FET. Field Effect Transistor (FET): a three-terminal, unipolar (only majority carriers), voltage-controlled semiconductor device in which the cur... 1