AD8603/AD8607/AD8609

Rev. B | Page 14 of 20

BATTERY-POWERED APPLICATIONS

The AD8603/AD8607/AD8609 are ideal for battery-powered

applications. The parts are tested at 5 V, 3.3 V, 2.7 V, and 1.8 V

and are suitable for various applications whether in single or

dual supply.

Figure 47 shows a simple photodiode circuit. The feedback

capacitor helps the circuit maintain stability. The signal

bandwidth can be increased at the expense of an increase in the

total noise; a low-pass filter can be implemented by a simple RC

network at the output to reduce the noise. The signal bandwidth

can be calculated by ½πR2C2 and the closed-loop bandwidth is

the intersection point of the open-loop gain and the noise gain.

In addition to their low offset voltage and low input bias, the

AD8603/AD8607/AD8609 have a very low supply current of

40 μA, making the parts an excellent choice for portable elec-

tronics. The TSOT package allows the AD8603 to be used on

smaller board spaces.

The circuit shown in Figure 47 has a closed-loop bandwidth of

58 kHz and a signal bandwidth of 16 Hz. Increasing C2 to 50 pF

yields a closed-loop bandwidth of 65 kHz, but only 3.2 Hz of

signal bandwidth can be achieved.

PHOTODIODES

Photodiodes have a wide range of applications from bar code

scanners to precision light meters and CAT scanners. The very

low noise and low input bias current of the AD8603/AD8607/

AD8609 make the parts very attractive amplifiers for I-V

conversion applications.

C2 10pF

R2 1000M

Ω

AD8603

Figure 47. Photodiode Circuit