In state-of-the-art implementations of instrument devices, a single amplifier stage may be required to provide a THD figure of better than -140 dB for a 5V RMS, 20 kHz signal in order to support a total instrument dynamic range of 120 dB in an 80 kHz measurement bandwidth. Currently it is not possible to achieve this performance level using available commercial monolithic operational amplifiers in a standard configuration. A proposed design approach achieves this goal. A unity gain stable composite operational amplifier is presented that consists of a cascade of two operational amplifiers, an intermediate compensation network and a frequency-selective feedback network for the second amplifier. This configuration achieves very high open-loop gain (100 dB at 100 kHz) and thus shows exceptionally good distortion characteristics. Furthermore, the noise characteristics of the first operational amplifier are preserved. The open-loop response is designed for conditional stability, such that a very-large-gain-bandwidth product at signal frequencies can be achieved. A numerical optimization procedure is then introduced to derive the frequency compensation, based on specific stability criteria. Measurement results confirm the predicted high-gain-bandwidth product (10 GHz at 100 kHz) and excellent distortion performance (-180 dB). Applications for the new composite operational amplifier include audio frequency distortion measurement equipment.
Click to purchase paper as a non-member or you can login as an AES member to see more options.
No AES members have commented on this report yet.
To be notified of new comments on this report you can
subscribe to this RSS feed.
Forum users should login to see additional options.
If you are not yet an AES member and have something important to say about this report then we urge you to join the AES today and make your voice heard. You can join online today by clicking here.
