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A circuit diagram of a buffer amplifier made using an operational amplifier. = = (realistically, the differential input impedance of the op-amp itself, 1 MΩ to 1 TΩ) Date: 26 January 2009: Source: Own work
A unity gain buffer amplifier may be constructed by applying a full series negative feedback (Fig. 2) to an op-amp simply by connecting its output to its inverting input, and connecting the signal source to the non-inverting input (Fig. 3). Unity gain here implies a voltage gain of one (i.e. 0 dB), but significant current gain is expected. In ...
Thus this circuit finds applications as a voltage buffer. In other words, the circuit has current gain (which depends largely on the h FE of the transistor) instead of voltage gain. A small change to the input current results in much larger change in the output current supplied to the output load.
The current gain is unity, so the same current is delivered to the output load R L, producing by Ohm's law an output voltage v out = v Thév R L / R S, that is, the first form of the voltage gain above. In the second case R S << 1/g m and the Thévenin representation of the source is useful, producing the second form for the gain, typical of ...
Feedback-free instrumentation amplifier is the high-input-impedance differential amplifier designed without the external feedback network. This allows reduction in the number of amplifiers (one instead of three), reduced noise (no thermal noise is brought on by the feedback resistors) and increased bandwidth (no frequency compensation is needed).
English: Circuit diagram of an SRAM cell, built with six MOSFETs. The bulk connection of all transistors is to ground, but is not shown from simplicity. The bulk connection of all transistors is to ground, but is not shown from simplicity.
Nonetheless, the voltage gain is appreciable even for small loads: according to the table, with R S = r E the gain is A v = g m R L / 2. For larger source impedances, the gain is determined by the resistor ratio R L / R S, and not by the transistor properties, which can be an advantage where insensitivity to temperature or transistor variations ...
Therefore, circuit simulators normally use more empirical models (often called compact models) that do not directly model the underlying physics. For example, inversion-layer mobility modeling , or the modeling of mobility and its dependence on physical parameters, ambient and operating conditions is an important topic both for TCAD (technology ...