REV. D

MAT04

–6–

TPC 11. Collector-to-Base

Capacitance vs. Collector-to-

Base Voltage

TPC 12. Collector-to-Substrate

Capacitance vs. Collector-to-

Substrate Voltage

TPC 10. Total Noise vs.

Collector Current

APPLICATION NOTES

It is recommended that one of the substrate pins (Pins 4 and 11)

be tied to the most negative circuit potential to minimize cou-

pling between devices. Pins 4 and 11 are internally connected.

APPLICATIONS

CURRENT SOURCES

The MAT04 can be used to implement a variety of high imped-

ance current mirrors as shown in Figures 1, 2, and 3. These

current mirrors can be used as biasing elements and load de-

vices for amplifier stages.

The unity-gain current mirror of Figure 1 has an accuracy of

better than 1% and an output impedance of over 100 M

Ω at

100

µA. Figures 2 and 3 show modified current mirrors de-

signed for a current gain of two, and one-half respectively. The

accuracy of these mirrors is reduced from that of the unity-gain

source due to base current errors but is still better than 2%.

Figure 4 is a temperature independent current sink that has an

accuracy of better than 1% at an output current of 100

µA to 1

mA. The Schottky diode acts as a clamp to ensure correct cir-

cuit start-up at power on. The resistors used in this circuit

should be 1% metal-film type.