OTA_four_quadrant_multiplier

Published:2009/7/24 23:51:00 Author:Jessie | From:SeekIC

This circuit uses all three sections of an OTA to form a four-quadrant multiplier. To adjust the circuit, remove all signals from the X and Y inputs, connect pin 10 to pin 8 (to disable amp 2), and set the Amp 1 offset to zero with the 100-kΩ potentiometer (adjust the pot until the output is zero). Disconnect pin 10 from pin 8, and connect pin 15 to pin 8 (to disable amp 1), and set the Amp 2 offset to zero with the corresponding 100-kΩ pot (adjust the pot until the output is zero). Disconnect pin 15 from pin 8. Apply equal ac signals to both the X and Y inputs. Adjust the 100-Ω and 200-kΩ pots for symmetrical output signals. Figure 11-2B shows the output waveform with the multiplier adjusted. The voltage waveform in Fig. 11-2Ba shows suppressed-carrier modulation of the 1-kHz carrier with a triangle wave. Figures 11-2Bb and 11-2Bc, respectively, show the squaring of a triangular wave and a sine wave. Notice that in both cases, the output are always positive and return to zero after each cycle.



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