Current sense amplifiers (also called current shunt amplifiers) are special-purpose amplifiers that output a voltage proportional to the current flowing in a power rail. They utilize a "current-sense resistor" to convert the load current in the power rail to a small voltage, which is then amplified by the current-sense amplifiers. The currents in the power rail can be in the range of 1 A to 20 A, requiring the current-sense resistor to be a resistor typically in the range of 1 to 100 mΩ. These amplifiers are designed to amplify a very small "sense voltage" of 10 to 100 mV, in the presence of very large common-mode voltages of 5 to 30 V. DC precision (low input offset voltage) and high
common-mode rejection ratio
In electronics, the common mode rejection ratio (CMRR) of a differential amplifier (or other device) is a metric used to quantify the ability of the device to reject common-mode signals, i.e. those that appear simultaneously and in-phase on both ...
(CMRR) are distinguishing characteristics of these amplifiers. Some current sense amplifiers measure current flowing in a single direction; bidirectional amplifiers measure current flow in both directions through the sense resistor.
Normal
differential amplifier
A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs V_\text^- and V_\text^+ and one outpu ...
s and
operational amplifier
An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to ...
s powered between two power supply rails (say ''V''
CC and ''V''
EE) can only handle signals that lie between these two power rails. If a voltage outside the power supply rails is applied to the input, internal ESD protection diodes turn on, causing large currents to flow and damage these parts.
Specialised current-sense amplifiers, by contrast are designed so that, when powered from a low-voltage power rail such as ''V''
CC = 5 V and ''V''
EE = 0 V, they can withstand pin voltages much higher than ''V''
CC and much lower than ''V''
EE. These amplifiers use specialized ESD structures that enable them to have this functionality. Their input stages are designed such that when the input common-mode voltage is much higher than ''V''
CC or much lower than ''V''
EE, the input amplifier stage powers itself from the input common-mode voltage instead of ''V''
CC or''V''
EE.
Examples of integrated current-sense amplifiers includ
INA240INA293LTC6101MAX4080TS1100
an
In special cases, no ''V''CC pin is required to accomplish current-sensing; th
MAX9938
is such a device.
See also
* Differential amplifier
A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs V_\text^- and V_\text^+ and one outpu ...
* Shunts (electrical)
* Sense Amplifier
References
External links
Current Sense Amplifier Products Current Sensing OverviewHigh-Side Current-Sense Measurement: Circuits and PrinciplesCurrent Sense Circuits and Applications
{{DEFAULTSORT:Current Sense Amplifier
Electronic amplifiers