Amplifiers – With d.c. reinsertion circuit
Reexamination Certificate
2000-06-15
2003-06-10
Shingleton, Michael B (Department: 2817)
Amplifiers
With d.c. reinsertion circuit
C330S069000, C330S146000, C330S150000, C327S307000
Reexamination Certificate
active
06577187
ABSTRACT:
BACKGROUND
This invention relates to preamplifiers for powered transducers such as condenser microphones, and in particular to such preamplifiers that directly couple the preamplifier input with the preamplifier output.
As is well known in the art, powered transducers such as condenser microphones are biased with a phantom voltage such as +48 VDC. It is customary to use a reactive component such as a capacitor or a transformer to isolate the preamplifier from the biasing voltage. Such reactive components can introduce a phase shift known as signal group delay which often varies as a function of frequency, thereby producing distortion.
The present invention is directed to an improved preamplifier for a powered transducer that substantially overcomes these drawbacks of the prior art.
SUMMARY
The powered transducer preamplifiers described below include a preamplifier circuit having a preamplifier input, a preamplifier output and a preamplifier signal path that DC couples the input and the output. A biasing circuit is coupled to the input to apply a DC bias voltage to the input, thereby powering the transducer, and a DC level shifting circuit is DC coupled to the signal path between the input and the output. This DC level shifting circuit compensates for the bias voltage by substantially or completely eliminating the bias voltage at the output.
Because the entire signal path between the preamplifier input and output is DC coupled, phase distortion associated with the capacitive and inductive components used in the prior art described above are completely eliminated.
A wide range of circuits can be used to implement the preamplifier circuit, the biasing circuit, and the DC level shifting circuit, as described in detail below. This section has been provided by way of introduction, and it is not intended to limit the scope of the following claims.
REFERENCES:
patent: 3595998 (1971-07-01), Fidi et al.
patent: 3761831 (1973-09-01), Foerster
patent: 4949580 (1990-08-01), Graham et al.
patent: 5032797 (1991-07-01), Mijuskovic
patent: 5589799 (1996-12-01), Madaffari et al.
patent: 5748751 (1998-05-01), Janse et al.
patent: 5751823 (1998-05-01), Strickland et al.
patent: 5808501 (1998-09-01), Ivanov
patent: 5977828 (1999-11-01), Hu et al.
That Corporation, “InGenius™ High-CMRR Balanced Input Line Receiver,” That 1200, 1203, 1206, pp. 1-10.
Burr-Brown® INA103, “Low Noise, Low Distrotion Instrumentation Amplifier,” printed in U.S.A., Mar., 1998, pp. 1-12.
Analog Devices, “Self-Contained Audio Preamplifier,” SSM2017, Analog Devices, Inc., 1997, pp. 1-8.
Jensen Transformers JT-115K-E, “Microphone Input Transformer,” 8/95, pp. 1-2.
Brinks Hofer Gilson & Lione
Shingleton Michael B
UpState Audio
LandOfFree
Powered transducer preamplifier with DC level shifting circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Powered transducer preamplifier with DC level shifting circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Powered transducer preamplifier with DC level shifting circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3154035