| 摘要 |
The invention provides an integrated amplifier whose gain factor is adjusted by means of an auxiliary amplifier . The gain factor is determined by the ratio of two on-chip resistors and by the ratio of the dimensions of transistors in long-tailed pair circuits in the signal amplifier to those of the transistors in the long-tailed pair circuit in the auxiliary amplifier. Both resistance ratios and ratios between complete circuits can be realised highly accurately in integrated circuits. As a result, the accuracy of the gain factor is great. In an embodiment of the invention the dimensions of the long-tailed pair circuits in the auxiliary amplifier and in the signal amplifier are the same. This achieves that if the adjusting voltages and adjusting currents of corresponding transistors in the long-tailed pair circuits are the same, the gain factor is over a large range independent of supply voltage and temperature.
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