Back to results
US 5,182,462 AGranted
Current source whose output increases as control voltages are balanced
AssigneeNational Semiconductor Corporation
InventorMichael E. Wright
Life of this patent
Estimating the term…
Abstract
A novel circuit is taught to provide a smooth current transfer function over a range of two input voltages, so that power can be supplied to an electronic circuit from more than a single power source. In one embodiment such power sources include a battery and an DC supply operated off the AC mains. Associated with each such supply is a current source designed to provide a reference current. This reference current is used to establish mirror currents from each of the power leads in order to provide the desired output current.
Claims2
A circuit comprising:
- a first power input lead of a first polarity;
- a second power input lead of said first polarity;
- a third power input lead of a second polarity;
- an output lead for providing an output current;
- a first current mirror circuit comprising:
- a first transistor having a first current handling lead coupled to said first power supply lead, a second current handling lead coupled to said third power supply lead, a third current handling lead coupled to said third power supply lead, and a control lead coupled to said third current handling lead;
- a second transistor having a first current handling lead coupled to said second power supply lead, a second current handling lead coupled to said control lead of said first transistor, and a control lead coupled to said control lead of said first transistor;
- and
- a third transistor having a first current handling lead coupled to said second power supply lead, a second current handling lead coupled to said output lead, and a control lead coupled to said control lead of said first transistor;
- and
- a second current mirror circuit comprising:
- a fourth transistor having a first current handling lead coupled to said second power supply lead, a second current handling lead coupled to said third power supply lead, a third current handling lead coupled to said third power supply lead, and a control lead coupled to said third current handling lead;
- a fifth transistor having a first current handling lead coupled to said first power supply lead, a second current handling lead coupled to said control lead of said first transistor, and a control lead coupled to said control lead of said fourth transistor;
- and
- a sixth transistor having a first current handling lead coupled to said first power supply lead, a second current handling lead coupled to said output lead, and a control lead coupled to said control lead of said fourth transistor.
12 more elements
A circuit comprising:
- a first power input lead of a first polarity;
- a second power input lead of said first polarity;
- a third power input lead of a second polarity;
- an output lead for providing an output current;
- a first current mirror circuit comprising:
- a first means for establishing a first current flow from said first power supply lead to said third power supply lead, having a control lead having a control voltage associated with said first current;
- means for mirroring current from said first power supply lead to said third power supply lead, having a control lead coupled to said control lead of said first means;
- means for mirroring current from said second power supply lead to said third power supply lead, having a control lead coupled to said control lead of said first means;
- and
- means for mirroring current from said second power supply lead to said output terminal, having a control lead coupled to said control lead of said first means;
- and
- a second current mirror means comprising:
- a second means for establishing a second current flow from said second power supply lead to said third power supply lead, having a control lead having a control voltage associated with said second current;
- means for mirroring current from said first power supply lead to said third power supply lead, having a control lead coupled to said control lead of said second means;
- means for mirroring current from said second power supply lead to said third power supply lead, having a control lead coupled to said control lead of said second means;
- and
- means for mirroring current from said first power supply lead to said output terminal, having a control lead coupled to said control lead of said second means.
14 more elements
Dependencies are inferred from the claim text.