Dual gate FET mixing apparatus with feedback means

• US 4,814,649 A
• Filed: 12/18/1987
• Issued: 03/21/1989
• Est. Priority Date: 12/18/1987
• Status: Expired due to Fees

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Young, James P.
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Callahan, Timothy P.
• Application Number:
  US07/134,656
• Time in Patent Office: 459 Days
• Field of Search: 307/529, 307/219.1, 307/304, 328/14, 328/15, 328/158, 328/20, 328/160, 330/277, 330/69, 330/290, 330/291, 331/116 FE, 331/117 FE, 455/332, 455/333
• US Class Current: 327/113
• CPC Class Codes: H03D 2200/0043 Bias and operating point
• CPC Class Codes: H03D 7/125 with field effect transistors

Abstract

When a dual gate FET is used in a mixing type circuit, the non-linear characteristics of an over-driven gate on the FET is used to create the sum and difference of the gate applied signals at the drain of the FET. Although feedback typically is used to increase the linearity of a class A amplifier where a single gate FET is used, the feedback in the present circuit overcomes the problem of maintaining a stable operating point for the mixer circuit while not interfering with the performance of the FET as a mixer. Thus, with the feedback to the first gate, the sensitivity of the DC bias on the second gate is decreased and can be set with simple (wide tolerance) components.

Claims

1. Signal mixer apparatus comprising, in combination:

dual gate FET first means including first and second gate means, source means and drain means;

constant current source second means connected to said drain means of said first means;

reference potential third means connected to said source means of said first means;

feedback impedance fourth means connected between said drain means and said first gate means of said FET first means;

signal source fifth means for supplying a first signal to be mixed to said first gate means of said FET first means;

signal source sixth means for supplying a second signal to be mixed to said second gate means of said FET first means; and

apparatus signal output seventh means, connected to said drain means of said first means, for outputting generated product signals.

2. Signal mixer apparatus comprising, in combination:

dual gate signal mixing solid state first means including first and second gate means, coupled between reference potential second means and signal output third means, said first means introducing non-linearities into resultant signals generated via a combination of signals applied to said first and second gate means and outputting same at said signal output third means;

current source fourth means connected to said signal output third means of said first means;

feedback impedance fifth means connected between said signal output third means and said first gate means of said solid state first means;

signal source sixth means for supplying a first signal to be mixed to said first gate means of said solid state first means; and

signal source seventh means for supplying a second signal to be mixed to said second gate means of said solid state first means.