Browse Prior Art Database

Precision microamps current generator

IP.com Disclosure Number: IPCOM000011579D
Original Publication Date: 2003-Mar-06
Included in the Prior Art Database: 2003-Mar-06
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Abstract

The problem to fix is, how to generate a precise microampere current generator.

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 100% of the total text.

Page 1 of 2

Precision microamps current generator

As described on figure 1, the normal way to generate a precise current is to use a voltage regulator, but the problem is that the voltage regulator need a minimum of current sink in order to bias its own internal circuits , and so the I output minimal becomes a few milliamps which is not correct in our application.

V input

 V oltage regulator

Vr RI output

I output # Vr / R

FIGURE 1

Our invention is based upon the capability of an operational amplifier (see figure 2) to stabilize the sum of the current on it's minus (-) lead . As its input impedance is very high, we can consider that at this lead we can have a virtual ground . The current I1 can be set by a fixed voltage generator : Vg. It can be calculated as : I1 = Vg /R1. The Rx resisor is the charge of our device needing a precise microamp current noted I2. As we know that I1 + I2 = 0, whatever the charge Rx, we will get the same mirroring micro current into Rx. A capacitor C is used to avoid any oscillation , and a buffer AOP2 to isolate the AOP1 circuit.

-

Rx

I2

C

R1

+Vg

+

-

I1

AO P1

AO P2

FIGURE 2

Disclosed by International Business Machines Corporation

1

[This page contains 8 pictures or other non-text objects]

Page 2 of 2

2