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However, a larger feedback resistance increases the output voltage swing, and consequently a higher gain from the operational amplifier is needed, demanding an operational amplifier with a high gain-bandwidth product. The feedback resistance and therefore the sensitivity are thus limited by the required operating frequency of the transimpedance ...
A transconductance amplifier (g m 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). These amplifiers are commonly seen installed in a cascode configuration, which improves the frequency response.
In high frequency circuits, impedance matching at the input and output of the amplifier is typically desired in order to eliminate signal reflections and maximize power gain. In the cascode, the isolation between the input and output ports is still characterized by a small reverse transmission term g 12 , making it easier to design matching ...
The OTA has a gain measured in units of transconductance whereas the Norton amplifier has a gain measured in units of transimpedance . [2] A commercial example of this circuit is the LM3900 quad operational amplifier and its high speed cousin the LM359 (400MHz gain bandwidth product). [3]
A transimpedance amplifier is a very sensitive broadband high-speed device featuring a feedback loop. This fact means the layout is plagued with stability problems and special compensation of PIN diode capacitance must be performed, therefore this doesn't allow selection of a wide range of cheap PIN photodiodes with varying capacitances.
VFAs have a gain/bandwidth dependence; CFAs have a transimpedance/feedback resistance dependence. In VFAs, dynamic performance is limited by the gain-bandwidth product and the slew rate. CFAs use a circuit topology that emphasizes current-mode operation, which is inherently much faster than voltage-mode operation because it is less prone to the ...
Modern Class AB amplifiers commonly have peak efficiencies between 30 and 55% in audio systems and 50-70% in radio frequency systems with a theoretical maximum of 78.5%. Commercially available Class D switching amplifiers have reported efficiencies as high as 90%. Amplifiers of Class C-F are usually known to be very high-efficiency amplifiers.
In a single-stage amplifier, one can increase channel length to get higher output resistance and gain as well, but this also increases the parasitic capacitance of transistors, which limits the amplifier bandwidth. The transistor channel length is smaller in modern CMOS technologies, which makes achieving high gain in single-stage amplifiers ...