| 摘要 |
A current mirror configuration can be integrated in the output stage of an operational amplifier that enables rail-to-rail performance without requiring a significant increase in headroom. The operational amplifier can be configured with a chopper stabilized current mirror configured within the output stage of the operational amplifier. Through use of the integrated current mirror in the output stage of the amplifier, the substrate of the integrated circuit can be suitably grounded to minimize noise problems. To obtain rail-to-rail output performance, the operational amplifier can incorporate a positive and negative charge pump. However, rather than requiring the negative charge pump to charge pump the operational amplifier negative for a full VGS voltage, such as in a conventional current mirror, the integrated current mirror requires minimal headroom for implementation with the operational amplifier. For example, the current mirror enables the charge pump to only charge pump the operational amplifier negative by approximately ½ VBE voltage so that the NMOS source-drain diffusions are not forward-biased to the grounded substrate.
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