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US 4,065,682 AGranted
Logarithmic converter
AssigneeMcIntosh Laboratory, Inc.
InventorRonald C. Evans
Life of this patent
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AssigneeMcIntosh Laboratory, Inc.
InventorRonald C. Evans
Estimating the term…
A system for deriving a voltage which is a logarithmic function of peak value of an audio signal, in which the audio input signal is amplified by means of an operational amplifier having bipolar feedbacks through a pair of oppositely poled rectifying junction devices operating over logarithmic portions of their response characteristics, the output of the operational amplifier being applied in opposite polarities to a second pair of rectifying junction devices to rectify a bipolar signal applied thereto, and to control current flow to a storage capacitor, the second pair of devices having a common load which provides a constant current source for slow charge of the storage capacitor in one sense, the second pair of devices providing rapid discharge paths in the opposite sense. In one embodiment either or both pairs of rectifying junction devices can be transistors. Improved operation occurs with transistors in that they exhibit gain as well as rectifying characteristics which increases the range of the inventive circuit.
A peak rectifying system for an AC signal comprising an amplifier of said signal, said amplifier having a bipolar output, a bipolr circuit including a first transistor and a second transistor, means biasing said transistors approximately to cut-off, a storage capacitor directly connected
In combination, a source of wide-band audio signal rapidly varying in amplitude, a logarithmic operational amplifier having an input connected to said source, an amplifying full wave rectifier means connected to the output of said amplifier, a storage capacitor connected as a load for said amplifying full wave rectifier means, said amplifying full wave rectifier means including means for rapidly increasing the charge on said capacitor in one sense in response to an increase in said wide band audio signal amplitude and means for slowly decreasing said charge in response to a decrease in said wide band audio signal amplitude.
A peak signal meter comprising an operational amplifier of said signal having a feedback circuit including a pair of oppositely poled rectifying junction devices, a bipolar full wave rectifying circuit connected in cascade with said amplifier including first and second multiterminal rectifying junction devices, a storage capacitor connected between a corresponding terminal of said first and second devices and ground, other terminals of said first and second devices responsive to said operational amplifier output, and a visual voltage transducing means connected to said storage capacitor.
Dependencies are inferred from the claim text.