BiCMOS operational amplifier for switch/capacitor circuits
AssigneeSiemens Aktiengesellschaft
InventorsGerhard Nebel, Georg Georgakos, Ulrich Kleine
Life of this patent
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Abstract
The operational amplifier which has a high input impedance as well as a high bandwidth, is designed particularly for capacitive loads and, above all, maintains its operating point within narrow limits irrespective of technological fluctuations. The BiCMOS amplifier uses bipolar cascades (Q6, Q16, Q7, Q17) as output paths which are driven at high impedance, via PMOS cascade transistors (M6, M7), directly by the differential amplifier transistor pair (M4, M5), as a result of which a current is output and the maintenance of the operating point of the operational amplifier is ensured even when technological fluctuations are taken into account.
Claims7
A BiCMOS operational amplifier for switched capacitor circuits, comprising
- an MOS differential amplifier stage, which is supplied with a reference current by a current source and which has a respective load element in each of two paths of the MOS differential amplifier stage;
- two output paths each of the two output paths having a respective series circuit formed by a respective further load element and two respective bipolar transistors, the respective bipolar transistors forming a cascade;
- the base of each of the bipolar transistors being supplied with a first reference voltage and one of the further respective load elements being connected to an output of the operational amplifier;
- a respective bipolar transistor of a respective cascade can be driven, via a respective PMOS transistor to whose respective gate a second reference voltage is applied, directly by a voltage across the respective load element of the respective path of the MOS differential amplifier stage.
Dependencies are inferred from the claim text.