Datasheet

4 Application information
4.1 Driving resistive and capacitive loads
These products are low-voltage, low-power operational amplifiers optimized to drive rather large resistive loads
above 2 k
Ω.
The TSV99x products are not unity gain stable. T
o ensure proper stability they must be used in a gain
configuration, with a minimum gain of -3 or 4.
However, they can be used in a “follower“ configuration by adding a small, in-series resistor at the output, which
drastically improves the stability of the device (Figure 15. In-series resistor vs. capacitive load when TSV99x is
used in follower configuration shows the recommended in-series resistor values). Once the in-series resistor
value has been selected, the stability of the circuit should be tested on the bench and simulated with the
simulation model.
Another way to improve stability and reduce peaking is to add a capacitor in parallel with the feedback resistor. As
shown in Figure 16. Peaking versus capacitive load, with or without feedback capacitor in inverting gain
configuration, the feedback capacitor drastically reduces the peaking versus capacitive load (inverting gain
configuration, gain = -2).
Figure 15. In-series resistor vs. capacitive load when
TSV99x is used in follower configuration
Figure 16. Peaking versus capacitive load, with or without
feedback capacitor in inverting gain configuration
4.2 PCB layouts
For correct operation, it is advised to add 10 nF decoupling capacitors as close as possible to the power supply
pins.
4.3 Macromodel
An accurate macromodel of the TSV99x is available on STMicroelectronics’ web site at www.st.com. This model
is a trade-off between accuracy and complexity (that is, time simulation) of the TSV99x operational amplifiers. It
emulates the nominal performance of a typical device within the specified operating conditions mentioned in the
datasheet. It helps to validate a design approach and to select the right operational amplifier, however
, it does not
replace on-board measurements.
TSV991, TSV992, TSV994 TSV991A, TSV992A, TSV994A
Application information
DS4975 - Rev 14
page 11/28