Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Temperature
Reexamination Certificate
2000-04-26
2002-03-19
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Temperature
C330S289000
Reexamination Certificate
active
06359498
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a temperature compensation circuit of an AGC (Automatic Gain Control) circuit and particularly to a temperature compensation AGC circuit which is capable of introducing a compensation voltage generating unit of the simplified structure for generating a temperature compensation voltage by adequately selecting a bias current value of a temperature compensation diode.
2. Description of the Related Art
In general, an electronic tuner comprises at least a high frequency amplifying stage for amplifying the received high frequency signal, a frequency converting stage for mixing frequencies of the amplified high frequency signal and a local oscillation signal to generate an intermediate frequency signal, an intermediate frequency amplifying stage for selectively amplifying the intermediate frequency signal, detecting (demodulating) stage for obtaining a modulated signal by detecting (demodulating) the amplified intermediate frequency signal, and a receiving signal selecting unit for selecting and setting the frequency of the local oscillation signal in order to receive the signal of desired frequency.
Moreover, even if the received high frequency signal level has changed to a large extent in such electronic tuner, an AGC (Automatic Gain Control) circuit is generally provided in view of controlling variation of the demodulated signal level output from the detecting (demodulating) stage to a comparatively small value. This AGC circuit forms an AGC voltage from the demodulated signal obtained by the detecting (demodulating) stage and supplies this AGC voltage to the high frequency amplifying stage or intermediate frequency amplifying stage. Moreover, the AGC circuit also operates to control the gain of the high frequency amplifying stage or the intermediate frequency amplifying stage with the supplied AGC voltage. Therefore, when the received high frequency signal level has changed, variation of the intermediate frequency signal level to be supplied to the detecting (demodulating) stage is compressed to a large extent.
FIG. 3
is a circuit diagram illustrating an example of the structure of AGC circuit to be used in the existing electronic tuner.
As illustrated in
FIG. 3
, the AGC circuit is composed of a detecting circuit unit
31
, a temperature compensation circuit unit
32
, and a differential amplifying unit
33
. The detecting circuit unit
31
is connected, at its input end, to an intermediate frequency signal input terminal
35
, to one input terminal of the differential amplifying unit
33
at its output terminal and to a power source terminal
36
at its power source supply terminal. The temperature compensation circuit unit
32
is connected to the power source terminal
36
at its power source supplying terminal and connected to the other input terminal of the differential amplifying unit
33
at its output terminal. The differential amplifying unit
33
is connected to the control terminal of the high frequency amplifying stage
34
at its output terminal. Moreover, the high frequency amplifying stage
34
is connected to the high frequency signal input terminal
37
at its input terminal, also connected to the high frequency signal output terminal
38
at its output terminal and connected to the power source terminal
39
at its power source supplying terminal.
Here, the detecting circuit unit
31
is provided with a detection diode
31
1
, a branching capacitor
31
2
, four resistors
31
3
,
31
4
,
31
5
,
31
6
and a coupling capacitor
31
7
and these circuit elements
31
1
, to
31
7
, are connected as illustrated in the figure. The temperature compensation circuit unit
32
is provided with a temperature compensation diode
32
1
, a branching-capacitor
32
2
, four resistors
32
3
,
32
4
,
32
5
,
32
6
, a variable resistor
32
7
and these circuit elements
32
1
, to
32
7
are connected as illustrated in FIG.
3
. The differential amplifying unit
33
is provided with an operational amplifier
33
1
, and a feedback capacitor
33
2
and these circuit elements
33
1
, and
33
2
are connected as illustrated in FIG.
3
. The high frequency amplifying stage
34
is provided with a double gate field effect transistor (FET)
34
1
, a load inductor
34
2
, two coupling capacitors
34
3
,
34
4
, resistors
34
5
,
34
6
, and a buffer resistor
34
7
, and these circuit elements
34
1
, to
34
7
, are connected as illustrated in FIG.
3
.
In this AGC circuit, a structure of the detecting circuit unit
31
is identical to a structure of the temperature compensation circuit unit
32
, except for the point that a variable resistor
32
7
is connected to the temperature compensation circuit unit
32
, and the detection diode
31
1
and temperature compensation diode
32
1
have the identical characteristics.
The AGC circuit in the structure explained above operates as explained below.
The power source voltage supplied to the power source terminal
36
is divided by the four resistors
31
3
,
31
4
,
31
5
,
31
6
and the divided voltage is then supplied to the detection diode
31
1
of the detecting circuit unit
31
as a bias voltage to set the operating point of the detection diode
31
1
. Moreover, in the temperature compensation diode
32
1
of the temperature compensation circuit unit
32
, the power source voltage supplied to the power source terminal
36
is divided by four resistors
32
3
,
32
4
,
32
5
,
32
6
and a variable resistor
32
7
and the divided voltage is then supplied to the temperature compensation diode
32
1
as a bias voltage to set the operating point of the temperature compensation diode
32
1
. In this case, the operating point of the temperature compensation diode
32
1
can be set identical to the operating point of the detection diode
31
1
by adjusting the variable resistor
32
7
.
When the intermediate frequency signal is supplied to the intermediate frequency signal input terminal
35
under the setting conditions explained above, this intermediate frequency signal is detected by the detection diode
31
1
of the detecting circuit unit
31
and moreover is smoothed by the branching capacitor
31
2
. Thereafter, this intermediate frequency signal is divided by a couple of resistors
31
5
,
31
6
and is then supplied to the inverted input terminal (−) of the operational amplifier
33
1
of the differential amplifying unit
33
as the first DC voltage. In addition, when the power source voltage supplied to the power source terminal
36
is also supplied to the temperature compensation circuit unit
32
, this power source voltage is then divided by two resistors
32
3
,
32
4
and the variable resistor
32
7
and is further divided by two resistors
32
5
,
32
6
through the temperature compensation diode
32
1
. Thereafter, this divided power source voltage is supplied to the non-inverted input terminal (+) of the operational amplifier
33
1
as the second DC voltage. The operational amplifier
33
differentially amplifies the first DC voltage and the second DC voltage supplied to two input terminals and generates the AGC voltage (positive voltage) including a differential voltage element of the first DC voltage and second DC voltage at the output terminal. This AGC voltage is then supplied to the high frequency amplifying stage
34
from the differential amplifying unit
33
.
When the AGC voltage is supplied to the high frequency amplifying stage
34
, it is then supplied to one gate of the double gate FET
34
1
via the buffer resistor
34
7
. In this case, the high frequency signal supplied to the high frequency signal input terminal
37
is then supplied to the other gate of the double gate FET
34
1
via the coupling capacitor
34
3
and is then amplified by the double gate FET
34
1
. The amplified high frequency signal is then supplied to the high frequency signal output terminal
37
via the coupling capacitor
34
4
.
Here, when the high frequency signal level to be input to the high frequency amplifying stage
34
becomes high, the h
Ikarashi Toshiya
Kurihara Yuji
Yamagata Yuichiro
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Callahan Timothy P.
Nguyen Hai L.
LandOfFree
Temperature compensation AGC circuit with temperature... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature compensation AGC circuit with temperature..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature compensation AGC circuit with temperature... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2841959