JP3155108B2 - Filter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter circuit used for selecting a frequency band in an infrared remote control receiver or the like, and more particularly, to a center frequency f of a band-pass filter.
_{The present} invention relates to a filter circuit having an adjustment circuit inside so that ₀ can be adjusted without using an external resistor.

[0002]

2. Description of the Related Art In an infrared remote control receiver, a signal frequency is selectively received using a bandpass filter in order to reduce the influence of disturbance light and other noises. Bandpass filters are integrated circuits (hereinafter referred to as "amplifier circuits").
IC). As a method of adjusting the center frequency f ₀ of the bandpass filter, a method using an external resistor is generally used. However, in order to reduce the number of parts,
It is preferable to incorporate a correction circuit inside the IC.

As a correction circuit inside the IC, a bar shown in FIG.
A low-pass filter has been proposed (JP-A-3-537).
No. 09). In FIG.
The resistance circuit 5 is a resistor R_AB, R_BC, R_CDSeries circuit and each resistor
R_AB, R_BC, R_CDZener dies connected in parallel to
Aether Z₁ , Z_Two , Z_Three It is composed of resistance
R _AB, R_BC, R_CDIs connected to one end of a resistor R_minThrough
And the other end is grounded. Usually
Anti-R_ABGrounding point, resistance R_AB, R_BCConnection point, resistance R _BC,
R_CDConnection point and resistance R_CD, R_minConnection point
Bonding pads G to J are provided respectively. Book
Capacitor C to body circuit 1₁The signal is input via
You. The main circuit 1 includes a capacitor C_TwoThrough the ground
Have been.

In this circuit, Zener diodes Z ₁ , Z ₂ , and Z are connected between two appropriate bonding pads G to J.
By passing an overcurrent through any one of the _three , any one of the Zener diodes Z ₁ , Z ₂ , and Z ₃ can be broken down to a short-circuit state. The Zener diodes Z ₁ , Z ₂ , and Z ₃ are selectively destroyed to adjust the resistance value.

[0005] Incidentally, as described in the publication, the body circuit 1, as shown in FIG. 5, the current mirror circuit 11 and a transconductance amplifier (hereinafter, referred to as g _m amplifier) 6,8, the buffer amplifier 7 , 9 and so on. The center frequency f ₀ is the transconductance g _m ,

[0006]

(Equation 1)

[0007] The current mirror circuit 10 forms a first constant current supply circuit 11 together with the center frequency correction resistance circuit 5 and the like. Assuming that the output current of the first constant current supply circuit 11 is I ₁ and the output current of the second constant current supply circuit 12 is I ₂ , g _m is calculated using a proportionality constant k,

[0008]

(Equation 2)

Can be expressed as If the resistance value of the center frequency correcting resistance circuit 5 changes, the output current I _{1 of} the first constant current supply circuit 11 changes, and the fact that the center frequency f ₀ also changes in the relation of (Equation 1) and (Equation 2) is used. Thus, the center frequency f ₀ is corrected. The publication also proposes a bandpass filter shown in FIG. This is the Zener diode Z
_The resistance value is adjusted by selectively cutting the metal wirings L _AB , L _BC , and L _CD using metal wirings L _AB , L _BC , and L _CD instead of ₁ , Z ₂ , and Z _3. .

[0010]

In such a conventional adjustment method, the Zener diode Z ₁ ,
Special processes such as short-circuiting of Z ₂ and Z ₃ and cutting of metal wirings L _AB , L _BC and L _CD are required. Therefore, in an IC process without any of these steps, an IC incorporating a correction circuit cannot be realized.

The present invention solves the above problems,
It is an object of the present invention to provide a filter circuit having a built-in center frequency correction resistor circuit that can be realized by a simple IC process without a special process.

[0012]

A filter circuit according to the present invention comprises a main circuit and a center frequency correction circuit coupled thereto.
Yes, the center frequency correction circuit
It consists of a current supply circuit. The constant current supply circuit includes a plurality of resistors each having one end commonly connected to each other and a bonding pad connected to each other end . Then, some or all of the plurality of bonding pads are electrically connected with bonding wires.
Connect to the lead connected to the
Adjust the output current value of the road to correct the center frequency.
ing.

[0013]

According to the filter circuit of the present invention, a part of or all of the plurality of bonding pads are connected to a power supply voltage by bonding wires in a normal bonding step.
Connected in common to adjust the output current value of the constant current supply circuit.
Thus, the center frequency can be corrected.

[0014]

An embodiment of the present invention will be described below with reference to FIG. This filter circuit is
And a center frequency correction circuit.
The wave number correction circuit is a constant current supply circuit connected to the power supply voltage.
Consists of One end of the constant current supply circuit is commonly connected to each other
And a plurality of resistors each having a bonding pad connected to the other end.
A resistance circuit for correcting the center frequency is provided. So
To partially or fully bond the bonding pads.
Common to leads connected to power supply voltage with binding wires
Connection to adjust the output current value of the constant current
The number is corrected. Below for center frequency correction
The configuration of the resistance circuit will be described. In Figure 1, the center frequency correction resistor circuit 2 connected to the main body circuit 1, the resistance R _A, R _B, are constituted by R _C. Each resistor R _A , R _B , R _C
Are commonly connected to each other, and the other ends are respectively connected to bonding pads A, B, and C. Each of the bonding pads A, B, and C is selectively connected to the power supply lead 3 by a bonding wire 4 as shown in FIG. In this embodiment, only the bonding pad A is connected to the power lead 3. Although the number of resistors is three, four or more resistors may be used for more accurate correction. 3 'is a ground lead and 3 "is an output lead.

FIG. 3 shows a configuration example of the first constant current supply circuit constituting the center frequency correction circuit . 2, only the bonding pad A is connected to the power supply lead 3. The voltage output from the reference voltage generation circuit 13 is V _ref ,
Assuming that the base-emitter voltage of the emitter follower transistor Q ₁ is V _BE and the power supply voltage is V _CC , the output current I ₁ of the first constant current supply circuit is

[0016]

(Equation 3)

## EQU1 ## Q_Two~ Q_FourIs Transis
It is. Resistance adjustment of center frequency correction resistance circuits 2 and 5
An example will be specifically described with numerical values. In FIG._AB
= 1kΩ, R_BC= 2kΩ, R_CD= 4 kΩ, this
The resistance value that can realize the center frequency correcting resistor circuit 5 is 0,
1 kΩ, 2 kΩ, 3 kΩ, 4 kΩ, 5 kΩ, 6 kΩ, 7
kΩ. On the other hand, in FIG. _A~
R_FAnd R_A= 7kΩ, R_B= 6kΩ, R_C=
5kΩ, R_D= 4kΩ, R_E= 3kΩ, R_F= 0, each
The bonding pads corresponding to the resistance are A, B,
Let C, D, E, F be:

[0018]

[Table 1]

The same effect can be realized by the combination of the above.

[0020]

As is evident from the foregoing description, according to the filter circuit of the present invention, it is possible to adjust the resistance value of the center frequency <br/> complement Seikai path in the wire bonding step of IC, short zener diode and wires cut also incorporates an adjustable center frequency complement Seikai path resistance in IC process without a process such as,
Adjust the output current value of the constant current supply circuit to compensate for the center frequency.
A filter circuit that can be corrected can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a bandpass filter according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method of adjusting the circuit of FIG. 1;

FIG. 3 is a circuit diagram showing a configuration example of a first constant current supply circuit of the circuit of FIG. 1;

FIG. 4 is a circuit diagram showing a configuration of a conventional bandpass filter.

FIG. 5 is a circuit diagram showing a configuration of a main circuit section of the circuit of FIG. 4;

FIG. 6 is a circuit diagram showing a configuration of another conventional bandpass filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body circuit 2 Resistance circuit 3 Power supply lead AC bonding pad

Continuation of front page (56) References JP-A-60-154654 (JP, A) JP-A-62-154664 (JP, A) JP-A-5-13686 (JP, A) JP-A-3-53709 (JP) , A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H03H 11/04

Claims (1)

(57) [Claims] 1. A filter circuit center frequency accessory Seikai path is coupled to the body circuit, the center frequency accessory Seikai path is made from the constant current supply circuit connected to the power supply voltage, before
The predetermined current supply circuit includes a plurality of resistors each having one end commonly connected to each other and a bonding pad connected to each other end, and a part or all of the plurality of bonding pads.
Lead connected to the power supply voltage by a bonding wire
Connected in common to adjust the output current value of the constant current supply circuit
A filter circuit for correcting the center frequency .