What Are Transistor Biasing Methods?

Current, feedback, dual feedback and voltage divider are all methods of transistor biasing. Transistor biasing, or the process of setting a transistor's DC operating voltage to the correct level, also includes the emitter feedback method.

Current biasing a transistor uses a fixed-current bias circuit where the base current remains constant. The biasing voltages and currents do not remain stable during operation, because temperature affects the operating point in this single-resistor type of biasing method.

Feedback biasing is a self-biasing configuration and is beta dependent. It requires two resistors to bias the transistor and has a collector to base feedback configuration. This type of feedback bias method is generally good for most amplifier designs.

Dual-feedback transistor biasing uses one more resistor than the feedback-biasing method. This improves stability by increasing the current flowing through the base bias resistors. The resistors provide both automatic biasing and feedback simultaneously.

The voltage-divider method utilizes a voltage-divider network to bias the common emitter. Two resistors are connected to the transistor's base terminal across the supply. This method makes the transistor circuit independent of changes and is the most widely used.

Transistor biasing with emitter feedback uses both collector base and emitter feedback to stabilize collector current. This method works best at lower power-supply voltages.