AD546JN AD [Analog Devices], AD546JN Datasheet - Page 6

• Manufacturer Part Number: AD546JN
• Description: 1 pA Monolithic Electrometer Operational Amplifier
• Manufacturer: AD [Analog Devices]

AD546
MINIMIZING INPUT CURRENT
The AD546 is guaranteed to have less than 1 pA max input bias
current at room temperature. Careful attention to how the am-
plifier is used will reduce input currents in actual applications.
The amplifier operating temperature should be kept as low as
possible to minimize input current. Like other JFET input am-
plifiers, the AD546’s input current is sensitive to chip tempera-
ture, rising by a factor of 2.3 for every 10 C rise. This is
illustrated in Figure 24, a plot of AD546 input current versus
ambient temperature.
Figure 18. Unity Gain Follower
Figure 21. Unity Gain Inverter
Figure 24. AD546 Input Bias Current vs
Ambient Temperature
Figure 19. Unity Gain Follower
Large Signal Pulse Response
Figure 22. Unity Gain Inverter
Large Signal Pulse Response
–6–
On-chip power dissipation will raise chip operating temperature
causing an increase in input bias current. Due to the AD546’s
low quiescent supply current, chip temperature when the
(unloaded) amplifier is operated with 15 V supplies, is less than
3 C higher than ambient. The difference in input current is
negligible.
However, heavy output loads can cause a significant increase in
chip temperature and a corresponding increase in input current.
Maintaining a minimum load resistance of 10 k is recom-
mended. Input current versus additional power dissipation due
to output drive current is plotted in Figure 25.
Figure 25. AD546 Input Bias Current vs.
Additional Power Dissipation
Figure 20. Unity Gain Follower
Small Signal Pulse Response
Figure 23. Unity Gain Inverter
Small Signal Pulse Response
REV. A