Browse Prior Art Database

REGULATED CURRENT SOURCE

IP.com Disclosure Number: IPCOM000008584D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-25
Document File: 2 page(s) / 74K

Publishing Venue

Motorola

Related People

Jeff Durec: AUTHOR [+2]

Abstract

In the application it is desired to generate a regulated current source which has a low sensitivity to loading. The application for the circuit is in 900 MHz cordless phones. In the application, a signal is received from an antenna, down converted to a lower frequency and demodulated and amplitied, so that the voice on the RF signal can be sent to the speaker.

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MOTOROLA .Technical Developments

REGULATED CURRENT SOURCE

by Jeff Durec and Eric Main

DISCLOSURE SUMMARY

BACKGROUND

  In the application it is desired to generate a regulated current source which has a low sensitivity to loading. The application for the circuit is in 900 MHz cordless phones. In the application, a signal is received from an antenna, down converted to a lower frequency and demodulated and amplitied, so that the voice on the RF signal can be sent to the speaker.

PRIOR ART

  The circuit depicted in Figure 1 is the common- ly used delta Vbe current regulator. The regulated output current is defined by Equation I. Where Al, A2, A3, A4 represent the respective areas of transis- tors Ql, Q2, Q3, 44. Additional mirrored outputs can be taken from the base of transistor 44 but this will load the structure causing deviations from Equation 1.

THE INVENTION

  In the invention depicted in Figure 2, two inte- grated feedback loops involving nine transistors establish a regulated current. The invention allows for mirrored outputs to be taken from the regulated output. The regulated output can be loaded with significant current exceeding ten times the quies- cent bias current with no discernible change in the regulated current output. Ideally you want to oper- ate with low power dissipation so the capability of establishing a large regulated output current with very little overhead current is useful. The base current loading of transistor J has practically no effect on...