Q.Mention any two biasing circuits.

For a transistor to work as an amplifier its emitter-base junction must be forward biased and its collector-base junction reverse biased, with the operating point held steady. Several standard biasing circuits arrange the required DC voltages, differing mainly in how well they hold the operating point against temperature changes and against variation of the current gain $\beta$. The four commonly used methods are:

1. Fixed bias (base bias) — a single resistor $R_B$ from the supply $V_{CC}$ sets the base current. It is the simplest arrangement but gives poor stability, because the operating point depends directly on $\beta$.
2. Collector-to-base feedback bias — the base resistor is returned from the collector rather than from the supply, providing negative feedback that improves stability over fixed bias.
3. Emitter feedback bias — an emitter resistor $R_E$ introduces current feedback that helps stabilise the operating point. …