JPH02267997A - Mounting structure for amplifier circuit - Google Patents

Abstract

PURPOSE:To suppress the effect of flux that is cut by a circuit on the inverting input side and one on the non-inverting input side, i.e., that of electromagnetic induction to a small extent by disposing the circuits on the inverting input side and that of non-inverting input side substantially in symmetry on the surface and rear of a printed wiring board. CONSTITUTION:Resistances 4 and 5 at the surface of a printed wiring board 14 and the resistances 6 and 7 at the rear of the above board are disposed in symmetry and similarly FETs 8 and 9 are disposed in symmetry at the surface and rear of the board 14. As input circuits at non-inverting and inverting sides are disposed substantially in symmetry at both the surface and rear of the printed wiring board, a loop that is subjected to electromagnetic induction is minimized to a certain extent that is caused only by the thickness of the above printed wiring board.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a mounting structure of an amplifier circuit mounted on a printed wiring board, and in particular, it relates to a mounting structure of an amplifier circuit mounted on a printed wiring board, and in particular, a mounting structure that minimizes the influence of electromagnetic flux. It is related to the mounting structure.

[Prior Art] Generally, a differential amplifier circuit has a circuit configuration as shown in FIG.

In Figure 2, 1 is a non-inverting input terminal, 2 is an inverting input terminal, 3 is a ground terminal (GND), 45.6.7 is a resistor, 8
．． 9 is an FET, 10 is a part of an internal amplifier circuit, 11 is a constant current circuit, and 13 is an output terminal.

In this circuit, when the human input signal is balanced, it is input between the terminals 1 and 2, but when it is unbalanced, it is input between the terminals 1 and 2.
or 2 is grounded. Here, an unbalanced case will be explained as an example, and the terminal 2 is grounded, and the terminal 1 in this case is connected to the signal input terminal 1.
I'll call it 2.

When this circuit is mounted on the printed wiring board 14, it will be configured as shown in FIG. 3, for example.

Further, a block diagram of the above-mentioned negative feedback amplifier circuit is generally represented as shown in FIG.

In FIG. 4, reference numeral 15 represents a transfer function in the input circuit section, which corresponds to the voltage division ratio of resistors 4 and 5 in the above example. 16 is a subtracter, FET8 and FE
This corresponds to the differential part by T9, and extracts only the function of extracting the difference component between the non-inverting input and the inverting input. 17 is a transfer function of the oven loop of the entire amplifier circuit, and corresponds to the degree of amplification at which the difference between the non-inverting input and the inverting input is amplified and transmitted to the output terminal 13.

18 is a transfer function in the negative feedback network, and corresponds to the voltage division ratio by the resistors 7 and 6.

[Problems to be Solved by the Invention] In the negative feedback amplifier circuit as shown in FIG. 15
And the transfer function 18 in the negative feedback network must be completely linear. Disturbances such as nonlinearity in the open loop transfer @, +7 of the amplifier circuit and electric 1 + f1 induction can be improved by negative feedback, but the input circuit Regarding the transfer function 15 in the section and the transfer function 18 in the negative feedback network, if there is nonlinearity or disturbance such as electromagnetic induction, it can no longer be expected to be improved by negative feedback.

Returning to the circuit of FIG. 2, the linearity of resistors 4-7 and the effect of the flux induced in the illustrated loop become an issue. The linearity of a resistor is rarely a problem as long as it is used with plenty of room for its rating, so the effects of electromagnetic induction are usually a problem.

The following examples can be given for devices with amplifiers.

That is, first, the power supply frequency and its high frequency appear in the amplified output due to the flux from the power transformer. Second, flux from circuits that actively charge and discharge capacitors (for example, power supply circuits, switching power supplies, etc.) jumps to them. Thirdly,
Pulsed noise from other equipment appears on the amplified output. Fourth, in a class B amplifier, the current route in the output stage always changes between the positive half cycle and the negative half cycle, so if the influence of the induced flux is unbalanced, it will be treated as even-order distortion. Appears in the output.

As mentioned above, if there is even a small area between the non-inverting side input circuit and the inverting side input circuit,
There is a problem in that electromagnetic induction as described above occurs in principle.

The present invention attempts to solve these problems. That is, an object of the present invention is to provide a mounting structure for an amplifier circuit that can minimize the influence of electromagnetic induction.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a differential amplifier circuit mounted on a printed wiring board, in which an inverting input side circuit and a non-inverting input side circuit are connected to the They are arranged substantially symmetrically on both sides of the printed wiring board.

[Function] According to the present invention, since the input circuit on the non-inverting side and the input circuit on the inverting side are arranged substantially symmetrically on both sides of the printed wiring board, the loop receiving magnetic induction in 1 is , it becomes a very small one that occurs due to the thickness of the printed wiring board.

[Embodiment] FIGS. 1(a) and 1(b) are perspective views showing an embodiment of the present invention.

The symbols in FIG. 1 correspond to the symbols in FIG. 3. That is, this embodiment is based on surface mounting on the premise that components and wiring patterns are arranged symmetrically on both sides of the flint wiring board 14. For example, the resistance 6.7 on the back side is symmetrical to the resistance 4, 5 on the front side of the printed wiring board 14, and the FE on the back side is symmetrical to the resistance 6.7 on the front side.
T9 is arranged symmetrically thereto.

Although the thickness of the printed wiring board 14 is exaggerated in FIG. 1 to make it easier to understand the arrangement of components on both sides, it is actually thin as shown in FIG. 3.

In this way, by symmetrically arranging components and wiring patterns on both sides of the printed wiring board 14, the parts and wiring patterns shown in FIG.
Can you see it? ! The loops subjected to magnetic induction are extremely small and occur due to the thickness of the printed wiring board 14.

In the above embodiment, from a microscopic perspective, the wiring pattern is slightly shifted on the back side (lower side) of the printed wiring board 14 in order to avoid the signal input terminal 12, so that both sides are not completely symmetrical. Although they are not arranged, to this extent it can be said that they are substantially symmetrical. Of course, if surface mount type terminals are used, it is possible to make the terminals completely symmetrical. Further, in the above embodiment, F is used as a differential amplification.
Although ET (discrete type) is used, transistors or operational amplifier ICs in which these are integrated may also be used. Further, although the description has been made using an unbalanced differential amplifier circuit, the present invention can be similarly implemented using a balanced amplifier circuit.

[Effects of the Invention] As explained above, according to the present invention, the circuit on the inverting input side and the circuit on the non-inverting input side are arranged substantially symmetrically on both sides of the printed wiring board. The influence of flux, that is, the influence of electromagnetic corrosion, can be minimized.

[Brief explanation of drawings]

Figures 1 (a) and (b) are perspective views showing one embodiment of the present invention, Figure 2 is an explanatory diagram showing an example of a conventional amplifier circuit, and Figure 3 is an example of mounting the amplifier circuit. FIG. 4 is an explanatory diagram similarly showing the amplifier circuit in a block diagram. 1...Non-inverting input terminal 2...Inverting input terminal 3...
・Ground terminal 4, 5, 6.7...Resistance 8.9・
...FET 12...Signal input terminal 13...
Output terminal 14...Printed wiring board. 4 others Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] 1. A differential amplifier circuit mounted on a printed wiring board, characterized in that an inverting input side circuit and a non-inverting input side circuit are arranged substantially symmetrically on both sides of the printed wiring board. Mounting structure of amplifier circuit.