Bandpass amplifier and receiver using bandpass amplifier
First Claim
1. A bandpass amplifier comprising a single stage operational amplifier, a bridged "T" network band elimination filter in a negative feedback path of said amplifier, and a phase shift correcting capacitor associated with said bridged "T" network band elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that said amplifier is stable.
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Accused Products
Abstract
The present application relates to an active bandpass amplifier comprising a single stage operational amplifier, a bridged "T" network single frequency elimination filter in the negative feedback path of the amplifier and a phase shift correcting capacitor associated with the bridged "T" network single frequency elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that the amplifier is stable. The bridged "T" network single frequency elimination filter in conjunction with the circuit capacities and phase shifts in the integrated circuits introduces a phase shift which would result in the amplifier oscillating when the network is placed in the feedback path and the corrective capacitor effects a corrective phase shift to render the amplifier stable. Such a bandpass amplifier allows high gain and high "Q" and the gain is many times higher than that of a conventional single stage amplifier where gain is typically limited to approximately 5 and the "Q" is limited to about 25. In the present case, this bandpass amplifier is capable of gains of greater than 10 and substantially higher "Q". Such an amplifier is advantageously used in a receiver and in a signalling system. The high gain capablility of the receiver is particularly advantageous in a mining environment where the receiver can be used as part of a signalling system.
28 Citations
37 Claims
- 1. A bandpass amplifier comprising a single stage operational amplifier, a bridged "T" network band elimination filter in a negative feedback path of said amplifier, and a phase shift correcting capacitor associated with said bridged "T" network band elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that said amplifier is stable.
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17. A bandpass amplifier comprising in combination a single stage operational amplifier, a bridged "T" network band eliminator filter, and a phase shift correcting capacitor,
said bridged "T" network band elimination filter cooperating with said single stage amplifier to provide negative feedback for said amplifier, said network and said amplifier introducing an undesired phase shift of the feedback signal, said correcting capacitor cooperating with said amplifier and said bridged "T" network band elimination filter to introduce a phase shift to compensate for the phase shift introduced by said bridged "T" network and said amplifier of sufficient magnitude to render said amplifier stable.
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19. A receiver comprising an antenna, a first bandpass amplifier, a mixer having an associated local oscillator, a second bandpass amplifier and detector means for determining whether a particular signal has been received,
said first and second bandpass amplifiers each comprising a single stage operational amplifier, a bridged "T" network band elimination filter in a negative feedback path of said amplifier, and a phase shift correcting capacitor associated with said bridged "T" network band elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that said amplifier is stable.
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24. A signalling system for use in alerting miners in underground mine comprising
means for generating an alarm signal at a low frequency for propogation through the mine, and a plurality of personal receivers each associated with a miner and operable from a portable battery supply carried by the miner, each receiver including an antenna tuned to the particular low frequency of the alarm signal and at least one bandpass amplifier comprising a single stage operational amplifier, a bridged "T" network band elimination filter in a negative feedback path of said amplifier, and a phase shift correcting capacitor association with said bridged "T" network band elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that said amplifier is stable, said at least one amplifier resulting in a gain in excess of 300 and "Q" in excess of 10, each personal receiver including alarm means associated with the output of said amplifier for indicating an alarm signal has been received.
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25. A signalling system for use in alerting miners in underground mines comprising
means for generating an alarm signal at a low frequency by applying the signal to the surface about a mine, and a plurality of personal receivers each associated with a miner and operable from a portable battery supply carried by the miner, each receiver including an antenna tuned to the particular low frequency of the alarm signal, a first bandpass amplifier, a mixer having an associated local oscillator, a second bandpass amplifier and detector means for determining whether said alarm signal has been received, said first and second bandpass amplifiers each comprising a single stage operational amplifier, a bridged "T" network band elimination filter in a negative feedback path of said amplifier, and a phase shift correcting capacitor associated with said bridged "T" network band elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that said amplifier is stable.
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31. In a communication system having at least one transmitter and at least one receiver wherein said receiver comprises an antenna, a first bandpass amplifier, a mixer having associated therewith a local oscillator, a second bandpass amplifier and detector means for determining whether a particular signal has been received,
said first and second bandpass amplifiers each comprising a single stage operational amplifier, a bridged "T" network band elimination filter in a negative feedback path of said amplifier, and a phase shift correcting capacitor associated with said bridged "T" network band elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that said amplifier is stable.
Specification