Current Sources and Voltage References

102

Modified current sources and example applications

Another way of performing multiplication or division of the reference current is by add-

ing resistors. This was alluded to previously when looking at Widlar’s circuits (see Fig-

ure 4.20). Now, if a resistor is inserted in series with the emitter of Q

2

in the divided

circuit in Figure 4.38, the output current ratio between the two devices is no longer

matched, but is divided and dependent on V

BE

and the value of the resistor. This is

also true for the multiplier circuit in which the reference current is multiplied, by putting

R

2

in series with Q

2

’s emitter. These circuits are reasonably resistant ...