Amplifying circuit
First Claim
1. An amplifying circuit high open loop gain for amplifying an input voltage signal to produce an output voltage signal, including an upstream first amplifying stage connected in cascade with a downstream second amplifying stage within an outer loop, said outer loop providing substantially linear amplification over an operating frequency range suitable for audio or instrumentation applications, whereinsaid second amplifying stage has connected thereto or associated therewith feedback means for providing that when said input voltage signal comprises a sinusoidal input voltage signal within an upper audible frequency range, an intermediate voltage signal measured at an intermediate point of the forward path of the amplifying circuit between the first and second amplifying stages is substantially phase advanced with respect to a notional non-advanced phase, the intermediate voltage signal remaining substantially phase advanced with current load.
0 Assignments
0 Petitions
Accused Products
Abstract
An amplifier is provided for audio or instrumentation applications which exhibits radically improved performance over existing amplifiers of comparable cost. In a preferred embodiment, the amplifier comprises two operational amplifiers (A1, A2) connected in cascade, where feedback elements (Cf2, Rf2) are connected across the second op amp (A2) to cause an intermediate voltage signal (Z) to be substantially advanced in phase. In this embodiment, a capacitor (Cf1) is also connected across the first op amp (A1), and an outer DC loop is provided with damping circuitry (Cf3) to reduce the closed loop gain at high frequencies, stabilizing the combination. The composite amplifier has performance far exceeding a conventional stand-along op amp and is very cheap to construct.
65 Citations
28 Claims
-
1. An amplifying circuit high open loop gain for amplifying an input voltage signal to produce an output voltage signal, including an upstream first amplifying stage connected in cascade with a downstream second amplifying stage within an outer loop, said outer loop providing substantially linear amplification over an operating frequency range suitable for audio or instrumentation applications, wherein
said second amplifying stage has connected thereto or associated therewith feedback means for providing that when said input voltage signal comprises a sinusoidal input voltage signal within an upper audible frequency range, an intermediate voltage signal measured at an intermediate point of the forward path of the amplifying circuit between the first and second amplifying stages is substantially phase advanced with respect to a notional non-advanced phase, the intermediate voltage signal remaining substantially phase advanced with current load.
-
17. A composite operational amplifier having improved stability and distortion, said composite amplifier comprising an upstream first operational amplifier connected in cascade with a downstream second operational amplifier, feedback means connected to the second operational amplifier such that the second operational amplifier acts as an integrator, and further feedback means connected to the first operational amplifier, and comprising a capacitor connected between the output and an input of the first operational amplifier, for providing that, in use, the composite operational amplifier may be placed within an outer loop of specified DC gain, and stabilising damping means connected to or associated with the outer loop in which the operational is placed to provide stable linear amplification.
-
18. A composite amplifier comprising:
-
an upstream first operational amplifier connected in cascade with a downstream second operational amplifier;
feedback means connected to or associated with the second operational amplifier;
further feedback means connected to or associated with the first operational amplifier;
an outer loop with resistive feedback to define a substantially linear amplification suitable for audio or instrumentation applications; and
outer loop damping means connected to or associated with the outer loop to reduce the gain of the composite amplifier at high frequencies;
said feedback means and further feedback means providing the composite amplifier with open loop gain substantially greater than the open loop gain of either operational amplifier and said outer loop damping means being adjusted so as to stabilise the composite amplifier. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
-
Specification