Back to results
US 5,859,569 AGranted
Current feedback differential amplifier clamp
AssigneeRaytheon Company
InventorsHieu M. Le, Lloyd F. Linder, Erick M. Hirata, Benjamin Felder, Roger N. Kosaka, Donald G. McMullin, Kelvin T. Tran
Life of this patent
Estimating the term…
Abstract
A current steering circuit diverts bias current from a differential current summing amplifier's front end when the differential input exceeds a safe threshold level, thus preventing the amplifier's output stage from being overdriven. Diverting the front end's bias currents also turns off transistors within the amplifier's front end and thus protects the front end from damage which may otherwise result from excessive input signals.
Claims9
A differential amplifier, comprising:
- a differential input stage having differential voltage inputs with said inputs connected to amplifiers with output terminals connected through a resistor at respective current feedback inputs, and
- a current clamp comprising:
- a comparison circuit connected to said differential input terminal to compare the voltage across said input terminals to a threshold value, comprising
- (i) a differential pair of transistors having a tail current, and
- (ii) a threshold circuit, said threshold circuit connected to provide voltages at the control terminals of said differential pair representative of a differential voltage appearing across the input terminals of said amplifier, with a threshold voltage added to said input differential input voltage, and
- a current diverting circuit connected to divert said amplifier's bias current and to be controlled in said diversions by said comparison circuit.
3 more elements
A subranging analog-to-digital converter comprising:
- a sample and hold circuit connected to receive and hold a differential analog signal,
- an analog-to-digital converter connected to receive the held analog signal from said sample and hold circuit and to convert said analog signal to a digital signal,
- a digital to analog converter connected to convert said digital signal from the analog to digital converter into an analog signal,and
- a differential amplifier connected to receive analog signals from said sample and hold circuit and from said digital to analog converter and to produce an analog signal based upon those inputs, said amplifier comprising:
- a differential input stage having differential voltage inputs with said inputs connected to amplifiers whose outputs are connected through a resistor at respective current feedback inputs, and
- a current clamp comprising:
- a comparison circuit connected to said differential input terminals to compare the voltage across said input terminals to a threshold value, and
- a current diverting circuit connected to divert said amplifier's bias current and to be controlled in said diversion by said comparison circuit.
5 more elements
A differential amplifier, comprising:
- a differential input stage having differential voltage inputs with said inputs connected to amplifiers whose output terminals are connected through a resistor at respective current feedback inputs, and
- a clamp circuit connected to divert bias current from the input stage when the voltage across the differential inputs exceeds a threshold value, wherein said clamp circuit includes a comparison circuit connected to said differential input terminals to compare the voltage across said input terminals to a threshold value, and a current diverting circuit connected to divert said amplifier's bias current and to be controlled in said diversion by said comparison circuit, wherein said comparison circuit comprises:
- a differential pair of transistors having a tail current, and
- a threshold circuit, said threshold circuit connected to provide voltages at the control terminals of said differential pair representative of a differential voltage appearing across the input terminals of said amplifier, with a threshold voltage added to said input differential input voltage.
1 more element
A method of protecting a differential amplifier from excessive input signals comprising:
- sensing the amplifier's input signal,
- in response to the sensed input signal exceeding a predetermined safe threshold value, diverting bias current from said amplifier to prevent it being damaged, and
- reverse biasing the base emitter junctions of transistors within the amplifier in response to sensed input signals exceeding a predetermined safe threshold value.
Dependencies are inferred from the claim text.