Normally input offset voltage is measured in the terms of input voltage applied at the non-inverting terminal to make output zero. Input offset voltage is symbolically represented by a voltage source that is in series with either the positive or negative input terminal (it is mathematically equivalent either way). FET-input op-amps tend to have lower input bias currents than bipolar-input op-amps, and hence incur less offset of this type. The voltage offset due to these currents is separate from the input offset voltage parameter and is related to the impedance of the signal source and of the feedback and input impedance networks, such as the two resistors used in the basic inverting and non-inverting amplifier configurations. For an analog DCOC (ADCOC), it is concluded that the PGA’s noise increases rapidly as. The analysis presented shows that the DCOC-induced noise may deteriorate the PGA’s noise performance significantly if we do not pay enough attention to it. Input bias current and input offset current also affect the net offset voltage seen for a given amplifier. The noise contribution of a DC offset cancelation (DCOC) circuit in a programmable gain amplifier (PGA) is studied for the first time in this paper. Chopper amplifiers actively measure and compensate for the input offset voltage, and may be used when very low offset voltages are required. However, the input offset voltage value may drift with temperature or age. This error can be eliminated using the external offset trim pot. This can be reduced to several microvolts if nulled using the IC's offset null pins or using higher-quality or laser-trimmed devices. However, the input offset voltage might not be zero. The input offset voltage ( V o s are around 1 to 10 mV for cheap commercial-grade op-amp integrated circuits (IC).
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