For comparison purposes, conventional field-effect transistor input and bias current compensated bipolar types are also listed. The third generation LTC1052 monolithic chopper-stabilized amplifier is significantly better than previous monolithic chopper-stabilized amplifiers in several areas. The chopping circuitry and sampled data operation of these amplifiers require significant attention for good results. The most significant tradeoff is increased complexity. This is the reason why chopper-stabilized amplifiers are able to achieve significantly lower time and temperature drifts than classic differential types. Because the DC input is translated to and amplified as an AC signal, the amplifier's DC terms have no effect on overall drift. This carrier, amplified and synchronously demodulated back to DC, furnishes the amplifier's output. The chopper-stabilized approach uses the amplifier's input to amplitude modulate an AC carrier. Jim Williams, in Analog Circuit Design, 2011 Publisher Summary While this technique provides DC accuracy and better frequency response, along with the flexibility of inverting and non-inverting configurations, it is prone to high levels of digital switching noise that may limit the usefulness of the wider bandwidth. Higher frequency signals bypass the nulling stage through feedforward techniques, making wide bandwidth operation possible. The output of the nulled stage is impressed on a storage capacitor so that when the cycle returns to the nulling phase (inputs shorted together), the output continues to reflect the last input voltage value.
#THE CHOPPER BUILDERS HANDBOOK SERIES#
In the output phase, the nulled input stage and the wideband stage in series amplify the signal. The feedback voltage is impressed on a storage capacitor so that during the second, or “output,” phase the offset remains nulled while the inputs are now connected to the signal of interest. During this nulling phase, amplified feedback is used to virtually eliminate the offset of the nulling stage.
In this approach, the inputs of the nulling stage are shorted together during the first phase of the operational cycle. These chopper-stabilized designs are capable of inverting operation only since the stabilizing amplifier is connected to the non-inverting input of the wideband amplifier. Since the main signal path is not sampled, the bandwidth of the system is determined by the bandwidth of the signal amplifier.
Auto-zero amplifier simplified schematicĬhopper-stabilized amplifiers solved the bandwidth limitations of the classic implementation by combining the chopper amplifier (used as a stabilizing amplifier) with a conventional wideband amplifier that remained in the signal path.
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