Biosignal Amplifiers – Biomedical Electronics

Flashcards covering key concepts from the lecture on Biosignal Amplifiers and Biomedical Electronics.

Voltage Amplifier

Amplifies an input voltage by a given gain factor (AV), described by Vout=AVVin.

Current Amplifier

Amplifies an input current by a given gain factor (AI), described by Iout=AIIin.

Transconductance Amplifier

Senses input voltage and produces output current proportional to this voltage, described by Iout=GVin.

Transresistance Amplifier

Senses input current and produces output voltage proportional to this current, described by Vout=RIin.

Input Resistance (Ri)

The resistance seen by the input signal, crucial for determining signal integrity in amplifiers.

Source Resistance (Rs)

The inherent resistance of the body or source that can affect amplifier performance.

Output Resistance (Ro)

The resistance encountered by the load at the amplifier's output.

Common-Mode Rejection Ratio (CMRR)

The ability of an amplifier to reject common signals, expressed in decibels (dB).

Ideal Operational Amplifier Characteristics

Includes infinite gain, zero offset voltage, infinite input impedance, and zero output impedance.

Slew Rate (SR)

The maximum rate of change of the output voltage of an op-amp, expressed in volts per microsecond (V/μs).

Gain Bandwidth Product (GBWP)

Indicates the frequency at which the amplifier provides a certain gain, key for determining bandwidth.

Monopolar Recording

A single site biopotential measurement with a single input channel.

Bipolar Recording

A dual site differencing measurement with two input channels used in biopotential measurements.

Noise Rejection

The ability of an amplifier to filter out unwanted signals, significantly important in biopotential measurements.

Instrumentation Amplifier

A type of amplifier designed for accurate low-level signals with high input impedance and high gain.

Inverting Amplifier

An amplifier configuration where the output is inverted and amplified, characterized by its feedback network.

Non-Inverting Amplifier

An amplifier configuration where the output is in phase with the input, allowing for higher input impedance.

Buffer Amplifier

Also known as a voltage follower, it isolates stages of a circuit without amplification.

Differential Amplifier

An amplifier that takes the difference between two input signals to produce an output.

Summing Amplifier

An amplifier that combines multiple input signals to produce a single output, typically inverted.

Voltage-controlled Voltage Source (VCVS)

A theoretical model in which the output voltage is controlled by an input voltage.

Design Resistance

The desired resistance value in an amplifier circuit necessary for achieving the required performance.

Transresistance Amplifier

An amplifier that senses input current to create output voltage across the load.

Impedance Matching

The practice of making the output impedance of one device equal to the input impedance of another to maximize power transfer.

Load Resistance (RL)

The external resistance or load the amplifier drives, critical for output calculations.

Active Components

Components that require an external power supply to operate, such as operational amplifiers.

Resistor Tolerance

The degree to which a resistor's actual resistance value may vary from its stated value.

Typical CMRR Values for Op-Amps

Common values range from 90dB for lower quality models to over 120dB for high precision amplifiers.

Clipping

The distortion that occurs when an amplifier attempts to output a voltage beyond its limits.

Voltage Gain (k)

The ratio of output voltage to input voltage in an amplifier, expressed as k = Vout/Vin.

Ideal Current Amplifier Characteristics

An ideal current amplifier should have low input resistance and high output resistance.

Design Considerations

Aspects to consider when designing amplifiers, such as resistor values, tolerances, and amplifier configurations.

Bridge Amplifiers

Circuits that provide methods for measuring changes in resistance, often incorporating differential measurements.

Voltage Follower Purpose

To provide impedance matching and isolation between different circuit stages.

Differentiator

An amplifier that produces an output proportional to the rate of change of the input signal.

Integrator

An amplifier that outputs a voltage signal proportional to the integral of the input voltage with respect to time.

Common Mode Signal

Signals that appear equally on both inputs of a differential amplifier, which can mask the desired signal.

AC and DC Coupling

Methods for connecting signals to amplifiers, with AC coupling removing DC levels and allowing AC signals.

Negative Feedback

Feedback in a circuit that reduces the gain of the amplifier, improving stability and bandwidth.

operational amplifier

the most common integrated circuit used for voltage amplification and a differential amplifier