Active RC filters

A resistor and amplifier-level technology, applied in the field of operational amplifiers, can solve problems such as signal delay effects, unfavorable low-power applications, and high-power feedback loops, and achieve low propagation delays, low power requirements, and reduced physical area.

Inactive Publication Date: 2017-08-29
NORDIC SEMICONDUCTOR
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this frequency compensation technique has an impact on the delay experienced by the signal as it propagates through the device
[0004] Feedback loops also tend to require considerable power and are therefore not well suited for low power applications such as battery powered portable devices

Method used

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  • Active RC filters
  • Active RC filters

Examples

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Embodiment Construction

[0028] figure 1 A circuit diagram of a first exemplary embodiment of an operational amplifier 2 according to the invention for use in an active RC filter is shown. The operational amplifier 2 comprises a first amplifier stage 4 and a second amplifier stage 6 .

[0029] The first amplifier stage 4 comprises a long tail pair transistor configuration comprising a differential pair of N-channel field effect transistors 8 , 10 and a tail transistor 12 . The differential pair of transistors 8 , 10 are connected via their respective source leads and then via tail transistor 12 to ground 44 . Each differential pair transistor 8 , 10 is also connected via its drain lead through a resistor 14 , 16 to a positive power supply 42 .

[0030]The second amplifier stage 6 also includes a long tail pair transistor configuration comprising a differential pair of N-channel field effect transistors 26 , 28 and a tail transistor 30 . The differential pair of transistors 26 , 28 are connected via...

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Abstract

An operational amplifier comprises: a first amplifier stage (4) comprising a first differential pair of transistors (8), arranged to receive and amplify a differential input signal (18, 20) thereby providing a first differential output signal (22, 24); and a second amplifier stage (6) comprising a second differential pair of transistors (26, 28) arranged to receive and amplify the first differential output signal (22, 24) thereby providing a second differential output signal (38, 40).

Description

technical field [0001] This invention relates to operational amplifiers, and in particular to those operational amplifiers suitable for use in active resistor-capacitor (RC) filters. Background technique [0002] Active RC filters, usually implemented as operational amplifiers, are commonly used analog filters, especially when implemented in integrated circuits. These filters generally exhibit good linearity and permit the use of signals with large amplitudes. However, these filters often have limited performance due to the inherent propagation delay associated with op amps. [0003] To stabilize an op amp, a technique called frequency compensation is often used. Frequency compensation involves using feedback to introduce a dominant pole into the transfer function of the system at a frequency just below the frequency associated with the next highest frequency pole. This dominant pole acts to reduce the gain of the amplifier to unity so that the existing pole does not caus...

Claims

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Application Information

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IPC IPC(8): H03F3/45
CPCH03F3/45188H03F3/45632H03F2200/297H03F2200/456H03F2200/453H03F2200/18H03F2200/234H03F2203/45562H03F2203/45631H03F2203/45434H03F2203/45424H03F2203/45406H03F2203/45512H03F2203/45528H03F2203/45174H03F2203/45201H03F2203/45202H03F2203/45208H03F2203/45264H03F2203/45036H03F2203/45051H03F2203/45088H03F2203/45101H03F2203/45134H03F2200/75H03F2200/555H03F2203/45652H03F2203/45644H03F2203/45702H03F2203/45694H03F2203/45682H03F3/45183H03F3/45475H03F2203/21112H03F2203/21157H03F2203/45084
Inventor 菲尔·柯比斯利
Owner NORDIC SEMICONDUCTOR
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