Digital Systems: Principles and Design

155Different Types of Logic Gates

EXAMPLES

In an RTL logic circuit, V

BE(ON)

is 0.7 V and input Voltage is 2.4 V. What is the base current

when the resistance in base-emitter circuit is 1 kW?

Solution

We use the equations I

B

= (V

i

 V

BE(ON)

)/R

B

= (2.4 V  0.7 V)/1000 W = 1.7 mA.

In an RTL logic circuit, V

BE(ON)

is 0.7 V and b forward current gain is 20. What will be

collector current in saturation state if I

B

= 1 mA?

Solution

We use the equation I

C

= bI

B

= b(V

i

 V

BE (ON)

)/R

B

= 20 ´ 1 mA = 20 mA

In an RTL logic circuit, find voltage output at the logic gate if V

BE(ON)

is 0.7 V and b forward

current gain is 10 and collector circuit resistance is 0.5 kW