Operational transconductance amplifier

In contrast to the traditional operational amplifier (OPA) an operational transconductance amplifier (OTA), Fig. 18, has a mode of operation where the non-inverting input is high ohmic whilst the inverting input is low ohmic. Here, the input current controls a current source, which affects transconductance and thus generates the output voltage [40,41]. 

In previous sections, we described the conventional op-amp and examined some of its applications. In this section, we survey other important operational elements—the current feedback op-amp (CFB), the operational transconductance amplifier (OTA), and the current conveyor (CC). All of these other operational elements are available commercially, and aU offer advantages and have some disadvantages in comparison with conventional op-amps such as the /xA741. Unlike the conventional op-amp, which is a voltage-controlled voltage source (VCVS) operational element, current is the main variable of interest at either an input or an output port of all the other operational elements. 

FIGURE 7.137 Operational transconductance amplifier (a) schematic representation, (b) ideal model... 

Figure 13 shows the schematic of the preamplifier, which is composed of an operational transconductance amplifier (OTA) and a feedback network. A capacitive negative-feedback amplifier is widely used in neural-recording systems [28] because there is usually a DC offset of 1—2 V across the electrode-tissue interface [29]. The gain of the amplifier is determined by the ratio of the two capacitances in the feedback network. 

Figure 7-19 Full-blown 4 Transconductance Operational Amplifier Compensation...

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