Q.Distinguish between FET and BJT.
[!TLDR]
FET: unipolar, voltage-controlled, very high input resistance, high switching speed, less noisy, easy to make in IC. BJT: bipolar, current-controlled, low input resistance, lower switching speed, more noisy, harder to make in IC.
| Sl. No. | FET | BJT |
|---|---|---|
| 1 | It is a unipolar device | It is a bipolar device |
| 2 | Current conduction is only by majority charge carriers (either holes or electrons) | Conduction is by both majority and minority carriers (both holes and electrons) |
| 3 | It is a voltage-controlled device | It is a current-controlled device |
| 4 | Input resistance is very high (of the order of several mega ohm) | Input resistance is very low (of the order of a few kilo ohm) |
| 5 | It has high switching speed | It has low switching speed |
| 6 | It is less noisy | It is more noisy compared to FET |
| 7 | Its fabrication is simpler in IC form | It is comparatively difficult to fabricate in IC form |
The most fundamental distinctions are the first three: a FET uses only one type of carrier and is controlled by the gate voltage, whereas a BJT uses both types of carrier and is controlled by the base current. The very high input resistance of the FET makes it especially useful in the input stages of amplifiers.
[!ANSWER]
FET — unipolar, voltage-controlled, very high input resistance, high switching speed, less noisy, easy to fabricate in IC. BJT — bipolar, current-controlled, very low input resistance, low switching speed, more noisy, harder to fabricate in IC.
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