Glossary of EE Terms
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Offset Error
Offset error is a measure of how well a converter’s actual transfer function matches the ideal transfer function at a single point. For a unipolar input data converter, the first code transition should occur at exactly one-half LSB above zero. For a DAC, with an input word of all 0’s, there should ideally be no analog output. Offset error is the deviation from these ideal states.
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Offset Matching
Offset Matching is expressed in mV. It is omputed using the following equation:
where OFFmax is the most positive offset error and OFFmin is the most negative offset error.
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Offset Voltage (V05)
The differential voltage needed across the op amp input terminals to obtain zero output voltage. Offset voltage values vary by process and design technology. Typical values are:
- Auto-Zero Op Amps <1µV
- Precision Op Amps: 50 µV to 500 µV
- Best Bipolar Op Amps: 10 µV to 25 µV
- Best JFET Iput Op Amps: 100 µV to 1000 µV
- Best Bipolar High Speed Op Amps: 100 µV to 2000 µV
- Untrimmed CMOS Op Amps: >2mV
- DigiTrim® CMOS Op Amps: <100 µV to 1000 µV
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Open-Loop Gain (AVO)
The ratio of the output voltage to the input offset voltage between the two input pins. The result is expressed in dB. Gain is usually specified only at dc (A1), but for many applications, such as high speed amplifiers for video and RF, the frequency dependence of gain is also important. For this reason the open loop gain and phase response is published for each amplifier.
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Operating Supply Voltage Range
The supply voltage range that can be applied to an amplifier for which it operates within specifications. Many applications implement op amp circuits with balanced dual supplies, while other applications use a single supply voltage. For example, battery power in automotive and marine equipment provides only a single polarity. Even line-powered equipment, such as computers, may have only a single-polarity built-in supply, furnishing +5V or +12V dc for the system, or often as low as 1.8V, with newer applications going even lower.
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Operational Amplifier
An integrated circuit voltage amplifier with two power pins non-inverting and inverting inputs and an output. Characteristics approach those of an “ideal” amplifier. These include infinite gain, bandwidth, and input impedance combined with no noise or output impedance.
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Optocoupler
An optocoupler is a traditional method of isolation utilizing LEDs and photosensitive transistors and/or diodes.
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Orientation
Orientation is the position in free space and is commonly identified as portrait/landscape. An accelerometer’s response to Earth’s gravitational field can be used to determine orientation.
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Orthogonal
Term used to signify that two signals (or signal attributes) are mutually transparent and non-interfering with each other. Frequency and amplitude modulation are orthogonal signal attributes.
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Orthogonal Plane
An orthogonal plane is a set of mutually perpendicular axes meeting at right angles.
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Oscillation
Oscillation is repetitive back and forth movement such as a vibration.
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Out of Range Recovery Time
Out of range recovery time is the time it takes for the ADC to reacquire the analog input after a transient from 10% above positive full scale to 10% above negative full scale, or from 10% below negative full scale to 10% below positive full scale.
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Over Sampling
Synthesis of an output frequency at a sampling rate above that which the Nyquist theorem would dictate.
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Overvoltage Protection
Industrial systems can be prone to line surges and voltages outside the operating limit of the ICs which may damage the devices if overexposed. Overvoltage protection is required to help prevent this and is usually implemented as a combination of discrete circuits and on-chip circuitry.
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