Page 404 - Op Amps Design, Applications, and Troubleshooting

380 ARITHMETIC FUNCTION CIRCUITS

FIGURE 9.16 Continued

9.6 TROUBLESHOOTING TIPS FOR ARITHMETIC CIRCUITS

Most of the arithmetic circuits presented in this chapter are electrically similar to
other amplifier circuits previously studied; it is the component values and
intended application that cause them to be classified as arithmetic. With this in
mind, all of the troubleshooting tips and procedures previously discussed for sim-
ilar circuits are applicable to the companion arithmetic circuits and will not be
repeated here.
Proper operation of the arithmetic circuits presented in this chapter requires
accurate component values. It is common to use precision resistors to obtain the
desired performance. If a component changes value, its effects may be more notice-
able in the arithmetic circuits than in similar, nonarithmetic circuits previously dis-
cussed. The very nature of the arithmetic circuit generally implies a higher level of
required accuracy than that for a simple amplifier. Thus, the probability of prob-
lems being caused by component variations is greater with arithmetic circuits.
To diagnose a problem caused by a component variation, it is helpful to
apply your theoretical understanding of the circuit to minimize the number of
suspect components. By applying various combinations of signals and monitoring
the output signal, you can usually identify a particular input that has an incorrect
response. If, on the other hand, all of the inputs seem to be in error (e.g., shifted
slightly), then the problem is most likely a component that is common to all inputs
(e.g., the feedback resistor or op amp).