| 摘要 |
A programmable gain preamplifier is provided which has a low temperature drift and good dynamic range characteristics. The programmable gain preamplifier provides a programmable gain of the difference between two input signals (Ain and Ain' for example). One of the input signals (Ain') may be an estimation of the other input signal (Ain). The estimation input signal (or a signal related to the estimated input) may be generated by the use of a reference voltage and a first resistor string. More particularly, the reference voltage and the first resistor string may operate as a digital to analog converter (DAC) that converts a digital estimation signal to an analog estimation voltage. The analog estimation voltage operates as an analog voltage that is a function of (or the same as) the analog Ain' estimation signal. The first resistor string may provide the estimation voltage without loading the resistor string. Thus, the first resistor string may be simultaneously utilized by other circuitry, such as for example, a downstream ADC. The programmable preamplifier gain may be set by the use of a second resistor string and digitally programmable switches. Contacts to the resistors strings may be placed outside of the current path of each resistor string to provide highly stable resistor strings having a very low temperature drift. In one preamplifier embodiment, some or all of the opamps may chopper stabilized opamps, at least one opamp may be a current feedback opamp, the resistor strings may be at least 64 resistors long and programmable gains from 1 to 32 may be provided.
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