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.
V
EE
V
CC
C2 10pF
R2 1000MΩ
R1
1000MΩ
AD8603
C1
10pF
04356-047
Figure 47. Photodiode Circuit
