Logarithmic temperature compensation for detectors
AssigneeAnalog Devices, Inc.
InventorVincenzo DiTommaso
Life of this patent
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Abstract
The intercept of a logarithmic amplifier is temperature stabilized by generating a signal having the form H log H where H is a function of temperature such as T/T0. The first H factor is cancelled, thereby generating a correction signal having the form Y log H. The cancellation may be implemented with a transconductance cell having a hyperbolic tangent function. The H log H function may be generated by a pair of junctions biased by one temperature-stable current and one temperature-dependent current. The pair of junctions and the transconductance cell may be coupled together in a translinear loop. A user-accessible terminal may allow adjustment of the correction signal for different operating frequencies.
Claims1
A temperature compensation circuit for a detector having an input signal, the temperature compensation circuit comprising:
- a first bias current source;
- a second bias current source;
- a third bias current source;
- a first junction having a first terminal connected to the first bias current source;
- a second junction having a first terminal connected to the second bias current source and a second terminal connected to a second terminal of the first junction;
- a first transistor having a first terminal connected to the third bias current source, a second terminal connected to the first terminal of the first junction, and a third terminal to output a first current;
- and
- a second transistor having a first terminal connected to the third bias current source, a second terminal connected to the first terminal of the second junction, and a third terminal to output a second current;
- where the first, second and third bias current sources generate bias currents that are independent of the input signal.
Dependencies are inferred from the claim text.