2)
it is ok to bias the L-17C inputs as low as -1.5 V; however, although the amplifier
may not saturate when overdriven if the inputs are biased low, thermal recovery
will be degraded.
This may or may not be a problem, depending on the application. In order to avoid any
such problems, we strongly recommend clamping to avoid overdriving the input amplifier,
as illustrated below.
When using tunnel diode detectors, the inverting (transimpedance) configuration of the
front-end amplifier is recommended because the tunnel detectors function more effectively
when working into a very low impedance. However, when using Schottky detectors, the
front-end amplifier can be used in either the inverting or non-inverting mode. Everyone
has their own favorite method of biasing and connecting Schottkys, so the connections
shown below are merely intended to illustrate the important points which relate to the use
of Schottkys with the L-17C. There are numerous other possibilities.
Fig. D1 (Inverting Configuration)
RF, R1 and R2 are chosen to give the needed gain, and R3 balances the input bias
current. The input capacitance is very low because of low input Miller capacitance, which
results from the 2-stage architecture of the front-end amplifier, so R1 + R2 can be up to
500 ohms.
Fig. D2 (Non-Inverting Configuration)
-D2-
 |
 |
 |
 |
 |