Transimpedance amplifiers with different feedback arrangements (I in indicates an ideal current signal source). (a) Transimpedance amplifier with a single-resistor feedback. (b) Transimpedance amplifier with a T-shaped feedback network.
The noise model of an amplifier suggested by Letzter and Webster,21 including a noiseless amplifier with gain A, an equivalent amplifier noise current generator i na , an equivalent amplifier noise voltage generator e na , and a noiseless source (the input signal source) resistor R with its noise voltage generator e n .
Common-source JFET amplifier with source degeneration and its performance. (a) Schematic of a single-transistor transimpedance preamplifier comprising a feedback loop (consisting of a feedback resistor R1 and a DC blocking capacitor C1) and a common-source JFET amplifier with source degeneration. (b) Computer simulated BF862 common-source amplifier (as shown in Fig. 3(a), but without the feedback loop) voltage gains and drain currents I D with different source resistors R S (R6 in Fig. 3(a)). (c) Schematic of the single-transistor transimpedance preamplifier with a T feedback network. (d) Measured transimpedance of the single-transistor transimpedance preamplifier with a T feedback network (schematic shown in Fig. 3(c)), where two resistance values of the source resistors R6 (47 Ω and 470 Ω) were tested to show the variation of the transimpedance according to the biasing condition change.
The AD8099 preamplifier and the AD8099 voltage amplifier (VA). (a) Schematic of the AD8099 preamplifier with a T feedback network. When the transistor Q1, capacitors C1, C2, and resistors R1–R4 are disconnected, the rest of the circuit forms an AD8099 VA, which can be used to match the output impedance of the single-transistor preamplifier to a 50-Ω transmission line in an FTMS system. (b) Measured transimpedance of the AD8099 preamplifier with three feedback systems: (i) a single 18-kΩ feedback resistor shunting a 0.8-pF capacitor; (ii) a single 4.7-MΩ feedback resistor; (iii) the T feedback network as shown in Fig. 4(a).
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