| 摘要 |
An attenuator control circuit (103) for controlling operation of a differential pair attenuator (101) to provide linear in decibels (dB) operation and temperature and process-independent operation. The attenuator control circuit (103) is coupled in parallel with corresponding control input terminals VIN+, VIN- of the attenuator differential pair Q1, Q2. The attenuator control circuit also includes a current control circuit Q5-Q7, (204) that sources a supply current to the control differential pair Q3, Q4. The attenuator control circuit also includes an amplifier (203) that controls current through the first current path of the control differential pair to maintain constant total current IC3, IC4, so that the first current path exhibits the desired exponential attenuation function. Since the control differential pair is coupled in parallel with the differential pair attenuator, the output current of the differential pair attenuator also exhibits the desired exponential attenuation function. Furthermore, the attenuator control circuit includes a temperature compensation circuit (201) that applies a temperature proportional voltage VCNT to compensate for temperature variations. |
