OPERATIONAL TRANSCONDUCTANCE AMPLIFIER THESIS

The difference between the currents into the two input terminals with the output held at zero. A typical cascode circuit biased by a current source. The slope of the output gives the slew rate of the amplifier. The separation specification describes part of the isolation between the op-amps inside the same package. Sanasi Ramanan for their time to review this manuscript. I retain all other ownership rights to the copyright of the thesis. In fact, if this stage is very fast then it might cause stability problems due to the closed loop formed with the transistor.

Sanasi Ramanan Committee Member Dr. Operation in the triode region will cause the behavior of the OTA to be nonlinear and will result in poor transient response as well as a loss in DC gain. We also looked under the scope upto which our concerned technology can be extended. Thats all achievable because the output voltage is controlled by the magnitude of the resistance attached to itsoutput. Print Reproduction Permission Granted: HSPICE forms the cornerstone of a suite of Synopsys tools and services that allows accurate calibration of logic and circuit model libraries to actual silicon performance. A complete stability analysis, high frequency behavior and settling behavior are described.

Also, in a folded-cascode design, there is an input differential pair and two separate current branches for the differential output. It is observed that this variation i. Two-stage OTA 8 This configuration needs a suitable compensation scheme to stabilize the amplifier.

Some work can be done to improve this aspect of the design. This technique has been used in this thesis to design an operational amplifier with a gain greater than 85 dB and a unity gain bandwidth greater than 80 MHz.

The average of the currents into the two input terminals with the output at zero volts. The AC response of the designed amplifier is shown in Figure 4.

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One of the various compensation circuits Rc, Cc is also shown in Figure 2. The amplifer presented in this work does not use an output stage.

operational transconductance amplifier thesis

Transconductxnce is the maximum output voltage that the op amp can deliver without saturation or clipping for a given load and operating supply voltage. Care has to be taken not to make the input pair too big to affect the bandwidth and at the same time making them big enough to provide enough transconductance and hence the gain.

The main stage used is the telescopic cascode differential amplifier. All these commonly used amplifiers shown in this chapter are fully differential, and might need common mode feedback circuits in practical applications.

A 90 dB, 85 MHz operational transconductance amplifier (OTA

Sometimes it is used to describe any fin-based, multigate transistor architecture regardless of number of gates. The reason why the gain of the single-stage OTA is low is that it has low output impedance.

For the designed circuit this range is found to be 0. A complete list of specifications is mentioned in Chapter 4, Section 4. Different op-amp configurations 2. This is a large value, of the order of several tens of megohms or more.

A 90 dB, 85 MHz operational transconductance amplifier (OTA

Cascode circuits are widely used in circuit design at places where high gain and high output impedances are required. When they were working according to the demands, they were connected to the main amplifier and the performance of the overall amplifier was verified.

operational transconductance amplifier thesis

This range is 1. In [17] a regulated cascode stage has been presented that increases the gain of a normal cascode stage without affecting the frequency behavior to a large extent.

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operational transconductance amplifier thesis

The phase margin of an lperational amp circuit is the amount of additional phase shift at the closed loop bandwidth required to make the circuit unstable 20 i. Positive feedback is used to enhance the gain of the amplifier in [2]. The gives the input common mode range of the circuit.

A 45 nm node and below scaling might require the use of new processing steps or new device concepts such as FinFETs.

A complete analysis of the circuit is presented in this thesis which shows how this circuit leads to a high gain and resistance at output. They will reduce the unity gain frequency of the overall amplifier since by adding operattional gain-boost amplifiers to the output side, extra capacitance and thereby some extra poles are added. The gate direction is at right angles to the vertical fin.

For instance, when designing integrated high-frequency active filter circuitry, an OTA, is often used which is a much simpler building block. If the outputs are to be used as inputs to another OTA, their common mode must first be adjusted using a common mode feedback circuit. Also a brief description of the various characteristics of an ideal operational amplifier is mentioned.

The increased complexity will reduce the speed in comparison to a single stage amplifier. It is therefore possible to achieve high speed and high gain at the same time. I have known Dr. Optimizing the circuit for both leads to contradictory demands.