| 摘要 |
PURPOSE:To attain both high-gain and high-frequency characteristics at a time and to obtain a high input impedance by combining a differential amplifier containing a pair of FETs and a pair of bipolar transistors. CONSTITUTION:The input signals are applied to gate electrodes of FETs Q1 and Q2, and a constant current source 7 is connected to source electrodes of those paired FETs Q1 and Q2 via resistances 5 and 6. Then the base voltage of a pair of bipolar transistors Q3 and Q4 are controlled via the resistances 5 and 6. The drain electrodes of the Q1 and Q2 are connected to collectors of the Q3 and Q4 in an X-shaped formation. When a differential amplifier has the optimum frequency characteristics, the corner frequency and the voltage gain are set at about 160MHz and at +6dB respectively. Thus the input offset voltage can be reduced down to about 1/2 for all comparators.
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