The technique which, unlike dual-ramp methods, is inherently bipolar, claims some other advantages, such as improved linearity, more rapid recovery from overloads, higher sensitivity and reduced noise due to the averaging of thousands of zero crossings during the measurement, as well as a true digital auto-zero subtraction from the next measurement, as compared with the more usual capacitive-stored analogue offset p.d. Zero is in the middle of the measurement range and the displayed result is proportional to the difference between the number of +δ q, -δ q events. voltage, and the capacitor is then discharged by a large number of small +δ q and -δ q quantities, the elemental discharges being sensed and directed by fast comparator/flip-flop circuits and the total numbers being stored. This principle 5 employs a pair of differential- input transistors used to charge a capacitor by a current proportional to the unknown d.c. MJ Cunningham MSC, PHD, MIEE, CEng, GL Bibby BSc, CEng, MIEE, in Electrical Engineer's Reference Book (Sixteenth Edition), 2003 11.7.1.2 Charge balancing Applications include linear amplification, mixers, product detectors, amplitude modulators, frequency multipliers, voltage-controlled oscillators, and disk or tape memory read amplifiers. Internal feedback is provided for linearity control, and external feedback is difficult to apply without severely degrading the bandwidth. These amplifiers are typified by a wide bandwidth (dc to VHF), moderate gain (less than 1000 times) and moderate common-mode rejection ratio (CMRR) (50 dB). The amplifier may consist of a single stage or two stages and usually has a low-impedance output stage. This common-mode rejection is useful in noisy environments. The basic differential amplifier consists of two identical input transistors connected to respond to the difference between two input signals while simultaneously blocking the identical part of these signals. Harold Hosack, in Reference Data for Engineers (Ninth Edition), 2002 Differential Amplifier
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