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] Feedbac

Method used

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  • Active RC filters
  • Active RC filters

Examples

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Example Embodiment

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

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

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

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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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