Advanced Qualification · A-002 Advanced components and circuits · A-002-004-005

How does the input impedance of a field-effect transistor (FET) compare with that of a bipolar transistor?

1. A One cannot compare input impedance without knowing supply voltage
2. B An FET has low input impedance; bipolar transistor has high input impedance
3. C The input impedance of FETs and bipolar transistors is the same
4. D An FET has high input impedance; bipolar transistor has low input impedance

Correct answer: D — An FET has high input impedance; bipolar transistor has low input impedance. From the official ISED question bank, verified word for word.

Why

A field-effect transistor controls current using an electric field, so almost no current flows into its input, creating very high input impedance. The full explanation — and one for every question — is in Pro.

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Advanced components and circuits: semiconductors, amplifier classes, oscillators, mixers, filters and digital logic.

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