Gilbert cell

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The Gilbert cell is an analog multiplier for currents. It was developed in 1968 by Barrie Gilbert , who was then working for Tektronix in Beaverton . The output current of the cell is an exact multiplication of the differential input currents. The Gilbert cell is z. B. used when mixing signals or in voltage-controlled amplifiers .

Function description

Basic circuit of a Gilbert cell

The circuit structure is similar to the differential amplifier , whereby the current of the constant current source can be changed via an input. The gain of the differential amplifier depends on the current of the constant current source. Since this is controlled, it is multiplied by the signal at the differential input. The differential stage is largely designed twice, only the load resistors (not shown in the picture) are exchanged in pairs and used together. The same signal is present at both stages. In this way, the currents that result from the amplification are compensated, otherwise the amplified input signals would appear at the output in addition to the product.

The Gilbert cell is a component or basis of many integrated circuits serving as a mixer stage or containing one , since it has carrier suppression and low distortion and the required symmetry of the components can be achieved particularly well through integration.

Special case

The control of the circuit can also be heavily overridden , the behavior now corresponds to the XOR gate of digital technology. This property posed a problem in later patent disputes, as the Gilbert cell was patented as an XOR gate and not as an analog mixer.

See also

Individual evidence

  1. Wes Heyward (W7ZOI), Rick Campbell (KK7B), Bob Larkin (W7PUA) - Experimental Methods of RF Design, ISBN 978-0-87259-879-9


Barrie Gilbert: A Precise Four-Quadrant Multiplier with Subnanosecond Response. In: IEEE Journal of Solid-State Circuits Vol. 3, No. 4. IEEE Solid-State Circuits Society, December 1968, pp. 365-373 , accessed August 21, 2010 (January 6, 2003 version).