Browse Prior Art Database

Registration Automatic Gain Circuits

IP.com Disclosure Number: IPCOM000082135D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Davis, DE: AUTHOR [+3]

Abstract

This circuit adjusts the magnitude of an analog signal to a predetermined amplitude.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 94% of the total text.

Page 1 of 2

Registration Automatic Gain Circuits

This circuit adjusts the magnitude of an analog signal to a predetermined amplitude.

The input signal is derived from an electron-beam scanning across a mark in the surface of a semiconductor wafer. Each scan on a particular wafer produces similar signals; however, a different wafer will produce a signal that is different in amplitude. This circuit samples the signal from the first scan on a wafer, and uses this information to adjust the signal on subsequent scans to the predetermined amplitude.

During the first scan, switches J and S are closed and K is open. This applies V1 to the Y leg of the multiplier and enables the peak detectors to store the peak values produced by the input signal X times V1.

After the first scan and before the second scan the peak detectors are gated off by opening switches S, and the algebraic sum of the outputs of the peak detectors are gated into the sample and hold circuit by control input H. This X' input is applied to the divider and forms the quotient: 10Z Over X' which is applied to the Y leg of the multiplier for all subsequent scans (K closed, J open).

Thus after the first scan on a wafer, the signals from the rest of the scans are adjusted to a predetermined value. This value does not change, even though the input signal from the first scan varies from wafer-to-wafer. This circuit automatically adjusts its gain, producing an analog output signal of constant amplitude from an input signal t...