BJT DC BIASING

For the BJT to be biased in its linear or active operating region, the following must be true:• The base-emitter

junction must be forward-biased

• The base-collector junction must be reverse-biased

Operation in cut-off, saturation and linear regions of the BJT characteristics are provides as follows:

1. Linear-region operation: Base-emitter junction forward biased Base-collector junction reverse-biased

2. Cutoff-region operation: Base-emitter junction reverse biased

3. Saturation-region operation Base-emitter junction forward biased Base-collector junction forward biased

FIXED-BIAS CIRCUIT

FORMULAS INVOLVEDBase-emitter Base-collector

EXAMPLE 1

Determine the following for the fixed-bias configuration.

a) IBQ and ICQ

b) VCEQ

c) VB and VC

d) VBC

EMITTER-STABILIZED BIAS CIRCUIT

Contains an emitter resistor to improve stability level over that of the fixed-bias configuration.

BASE EMITTER LOOP

COLLECTOR-EMITTER LOOP

EXAMPLE 2For the emitter bias network, determine:

a) IB

b) IC

c) VCE

d) VC

e) VE

f) VB

g) VBC

VOLTAGE-DIVIDER BIAS

Determine the dc bias voltage VCE and the current IC.

COLLECTOR FEEDBACK

BASE-EMITTER LOOP

COLLECTOR-EMITTER LOOP

EXAMPLE 4

Determine Ic and VCE

EMITTER-FOLLOWER CONFIGURATION

EXAMPLE 5

Determine IE and VCE

COMMON-BASE CONFIGURATION

EXAMPLE 6Determine:

a. IE

b. IB

c. VCE

d. VCB