For example, a transconductance amplifier has a gain with units of conductance ( output current per input voltage ).

Such is the case with the operational transconductance amplifier, which has an open-loop gain ( transconductance ) in Siemens ( mhos ), because the gain is a ratio of the output current to the input voltage.

For translinear circuits, in which the exponential I – V curve is key to the operation, the transistors are usually modelled as voltage controlled with transconductance proportional to collector current.

This impedance reduces the overall transconductance of the circuit by a factor of, which makes the voltage gain

It also results in higher transconductance, which is a measure of the anode current change versus grid voltage change.

Conductance is the reciprocal of resistance ; transconductance, meanwhile, is the ratio of the current change at the output port to the voltage change at the input port.

For vacuum tubes, transconductance is defined as the change in the plate ( anode )/ cathode current divided by the corresponding change in the grid / cathode voltage, with a constant plate ( anode )/ cathode voltage.

Similarly, in field effect transistors, and MOSFETs in particular, transconductance is the change in the drain current divided by the small change in the gate / source voltage with a constant drain / source voltage.

A transconductance amplifier ( gm amplifier ) puts out a current proportional to its input voltage.

In network analysis, the transconductance amplifier is defined as a voltage controlled current source ( VCCS ).

They span a wide range of voltage gain and transconductance.

In electronics, a common-source amplifier is one of three basic single-stage field-effect transistor ( FET ) amplifier topologies, typically used as a voltage or transconductance amplifier.

The common-source ( CS ) amplifier may be viewed as a transconductance amplifier or as a voltage amplifier.

As a transconductance amplifier, the input voltage is seen as modulating the current going to the load.

However, the FET device's output resistance typically is not high enough for a reasonable transconductance amplifier ( ideally infinite ), nor low enough for a decent voltage amplifier ( ideally zero ).

That also reduces the potential voltage amplification obtainable from a triode compared with a pentode of the same transconductance, and usually means a more efficient output stage can be made using pentodes, with a lower power drive signal.

High transconductance tubes develop significant grid currents even with small negative bias ; in these cases, maximum instant voltage ceiling is lowered to-1. 0 ..- 0. 5 Volt.

The voltage-control model requires an exponential function to be taken into account, but when it is linearized such that the transistor can be modelled as a transconductance, as in the Ebers – Moll model, design for circuits such as differential amplifiers again becomes a mostly linear problem, so the voltage-control view is often preferred.

The origin of the term transistor is a contraction of " transconductance varistor ", proposed at Bell Telephone Laboratories, sometimes incorrectly attributed to a contraction of transresistance.

The transconductance for the bipolar transistor can be expressed as

The single transistor example shows how the method works in principle for a transconductance amplifier, while the second two-transistor example shows the approach to more complex cases using a current amplifier.

These are frequently described as operational transconductance amplifiers ( OTAs ) and normally have an input to allow the transconductance to be controlled.

With this relationship it is clear that the limits T → 0, or ∞ are realized if we let transconductance g < sub > m </ sub > → 0, or ∞.< ref > Although changing R < sub > D </ sub > // r < sub > O </ sub > also could force the return ratio limits, these resistor values affect other aspects of the circuit as well.

* Variable transconductance (" vari-mu ", " remote-cutoff " or " super-control ") tubes in general are those with a non-uniform grid wire spacing to allow them to handle a wide range of input signal levels without excessive cross-modulation distortion, and so useful in Radio frequency stages where Automatic gain control is applied to the pentode.

Valve electrometers use a specialized vacuum tube ( thermionic valve ) with a very high gain ( transconductance ) and input resistance.

** 1LC6-Similar to type 1LA6, but with higher conversion transconductance.

** 12GA6-Similar to type 12FA6, but with lower conversion transconductance.

* 6BY6-Similar to type 6CS6, but with higher transconductance.

The input stage of modern amplifiers is usually a differential amplifier with a transconductance characteristic.

Using the Shichman – Hodges model, the transconductance for the MOSFET can be expressed as ( see MOSFET article ):

Mataré had first observed transconductance effects during the manufacture of germanium diodes for German radar equipment during World War II.

* The amplifying element is biased so the device is always conducting to some extent, normally implying the quiescent ( small-signal ) collector current ( for transistors ; drain current for FETs or anode / plate current for vacuum tubes ) is close to the most linear portion of its transconductance curve.

Because of this exponential relationship, the BJT has a higher transconductance than the FET.

The device logically belongs in the varistor family, and has the transconductance or transfer impedance of a device having gain, so that this combination is descriptive.

The JFET has higher transconductance than the MOSFET and is therefore used in some low-noise, high input-impedance op-amps.

Many power valves have good linearity but modest gain or transconductance.

This had the effect of increasing the plate-grid distance for a given tube size, increasing the transconductance of the tube and reducing its noise figure.

Adding the suppressor allowed Sylvania to lower the current of the 6. 3 volt heater from 320 milliamperes to 150 milliamperes while maintaining the same conversion transconductance ( 550 microsiemens ).

Due to low relatively conversion transconductance ( 350 µmhos ), this valve is always fed by at least one tuned RF amplifier.

The noise figure of a valve is inversely proportional to its transconductance ; higher transconductance generally means lower noise figure.

The transconductance is typically very high — this is where the large open loop gain of the amplifier is generated.

Transresistance, infrequently referred to as mutual resistance, is the dual of transconductance.