JPS5962206A - Gain adjusting circuit - Google Patents

Abstract

PURPOSE:To attain the minute gain adjustment over a multi-stage by constituting a variable resistor section of a gain adjusting circuit with a resistor circuit network of series connection of plural resistors having a short-circuiting/opening means and that of parallel connection. CONSTITUTION:A feedback loop of an operational amplifier 3 consists of a series connection variable resistance network 4 comprising polysilicon fuses F21-F23 and resistors R21-R23 and a parallel connection variable resistance network 5 comprising polysilicon fuses F24, F25 and resistors R24-R25. Since the gain of this circuit is 1+(resistance value of resistance network 4 / resistance value of resistance network 5), the gain is increased when the fuse of the resistance network 4 is blown and the gain is decreased when the fuse of the resistance network 5 is blown. In setting the resistance value to a suitable value, the gain is adjusted into 24-stage.

Description

[Detailed description of the invention] The present invention relates to a gain adjustment circuit.

In analog integrated circuits, the circuit benefit q<+ ′ff
- A gain adjustment circuit is used for precise adjustment.

For this gain adjustment circuit, for example, one antibody is applied to a polysilicon 41 with polysilicon fuses at both ends.
4.1. From the variable proximity of the two series valves, the resistance network divided by a fixed resistor, and the amplification H::
A four-point adjustment circuit constructed in the art is commonly used. However, in this circuit, the fuse (JJ ttlli
In order to increase the resistance value of the variable resistance section for υ, it is possible to increase the resistance value (even if the resistance value after the change becomes too large than the value of 75T, further adjustment cannot be made, so the advantage of the circuit is 11). There is a problem in that the voltage becomes too large and the integrated circuit has a low V-output voltage which is considered defective.

Furthermore, when it is desired to fine-tune the desired gain fd by cutting the fuse, it is easily influenced by the resistance of the polysilicon phase shorted across the polysilicon resistor, making it difficult to precisely fine-tune the gain to the desired value. There is a problem that it is Lllj.

Below, these problems will be explained in detail regarding a specific circuit (+11).

FIG. 1 shows a circuit diagram of a conventional gain adjustment circuit formed using a silicon gate MOS device.

This circuit configuration as a whole forms a negative feedback amplifier 1q+', and the feedback loop of the amplifier 1 includes polysilicon fuses Fo to F13 and resistors f, n', Rt1 to ■.
Series-connected variable 11 consisting of 13 wires (2 wires and 1 fixed wire)
1 (has an anti-Iζ1 degree, and by changing the resistance value of the variable resistor network 2, the gain can be changed by changing At:in).

For setting the gain, polysilicon fuses F11 to F1g, which are set by polysilicon trimming H4≠, are used.

Resistors R11-R13 are connected in series J'j;, 1t5i:, and each resistor is connected to a polysilicon fuse F1t-F.
13), both ends are short-circuited. Polysilicon・
Fuse Fil~F13's own resistance I111 is all Q'
If LL, < Rf, resistor R11 and polysilicon heats F.

The resistance value of the parallel circuit part of is 1, the fuse [XI [+ is the parallel resistance of lht and Fil before
The same applies below. ), but fuse Lj, l break 1
No, - is the resistance of Jp1, 1 and 11 only, that is, Rn
Then, the fuse was cut! , l(R++ −R11/
Similarly, in the parallel circuit section of resistor R12 and polysilicon film F1°, the resistance increases by (R1
2-R12//Rf)s sum-resistor R+3 and polysilicon fuse F13 in parallel circuit part (R13-R
The resistance increases by r3//Rf). At this time, K (Rn - Rn // lef) - ΔR and 1
When flI was (R12-R12//R1' l
"2ΔR1(R13-Rt3//Rf) -4Δ
In order to lengthen the relationship R, the resistance value of the resistor Ru-R13 is Ii:>'iJl.

Therefore, the resistance value of variable resistor network 2 consisting of polysilicon fuses Ftx to F13 and resistors R11 to Rta to hjl is initially (R11/;/Rf + R12//Rf +
] and t3//Rf), but the fuse Fil is turned off.
If the fuse F1g is cut, the resistance will increase by ΔR; if the fuse F12 is cut, the resistance will increase by 2ΔR; if the fuse F1g is cut, the resistance will increase by 4ΔR;
Eight resistance values can be selected in increments of ΔR depending on the combination of fuse cutting.

The gain of the circuit at this time, V otrr / V m, is increased by cutting the fuse to 53@'''t (by changing the resistance value of resistor 2, the gain can be adjusted in 8 steps as shown in Table 1). can do.

Table 1 16”” R□□/ J + n1*7B, +1.
1. / n-1 As mentioned above, if the polysilicon fucose is cut (TJ ↓), the resistance f1rJ of the series-connected variable resistance value becomes J7
1L, the gain increases, but if the gain increases too much, this circuit configuration has no other means, so I
It is not possible to reduce the II gain, and the device becomes defective, resulting in a decrease in yield. Also, fine! If you want to adjust the value by 1%, you can reduce the minimum adjustment value ΔIt-i by using the variable resistance network fuse itself. ”;l
However, when the resistance value of the polysilicon resistor approaches the resistance value of the polysilicon fuse itself, the influence of the resistance value of the polysilicon fuses short-circuited across it becomes large. In other words, the change in resistance value before and after cutting the polysilicon fuse ΔR=(R-R/R
t) However, since polysilicon fuses are generally thin in shape, the shape may vary considerably due to the manufacturing of polysilicon fuses. ) followed by 1, slight:
It becomes difficult to set r, 1.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional art, and therefore, an object of the present invention is to make it possible to decrease the gain instead of increasing the gain in a gain II adjustment circuit. It is an object of the present invention to provide a gain adjustment circuit which allows fine adjustment to be made by 11 times without being affected by manufacturing conditions.

The circuit of the present invention consists of a series of resistors each having a short-circuiting/opening means for short-circuiting or opening both ends. The amount of change in resistance f1r1 is 2 iH = 1 j2 consists of a resistor network in which a plurality of resistors connected in series with the short-circuiting/opening means are connected in parallel. Parallel 4z: Eno'+: type ↑ variable resistance &
11 ('1'+
It consists of a vessel and 4-Q-i, +.

Hereinafter, regarding the present invention, with reference to the 1st I plane, 1°, 1111
I will explain the first part.

FIG. 2 is a circuit diagram showing one embodiment of the present invention, and includes five polysilicon fuses.
Possible Eu-level gain adjustment, circuit example/.

F21 to F25 each indicate a polysilicon fuse,
R21 to R25 are resistors formed of polysilicon resistors, and these resistors Ill'+1 are R21 to R25, respectively.
25. 3 is q amplification;! :'i'L
'be.

This embodiment forms a negative feedback amplification number as a whole,
i″fg, ￥J, Masanaka・``, 'Vessel 3 and its return 1 /
A series-connected variable resistor 4 consisting of polysilicon fuses F21 to F23 and resistors R21 to R23 forming a resistance division as a loop, and a polysilicon fuse F
24~F25 and polysilicon resistor: R24+R25
It consists of a parallel-connected nJ variable resistor network 5.

The gain of the amplifier can be increased or decreased by the oJ variable resistor networks 4 and 5.

i: IJ Take (((Anti-net 4 has resistance R21~lζ23 force m
They are connected in columns, and each resistor is short-circuited at both ends by polysilicon fuses F'21 to F23. In the variable resistance network 5, a series of polysilicon resistors F241F25 are connected to each resistor R241R25, and these resistor circuits connected in series V':f are connected in parallel.

Assuming that the resistance values of polysilicon fuses F21"'-F25 are all equal R4, the initial resistance value of the parallel circuit section 5) of resistor R21 and polysilicon fuses F21 is R2□ before the fuse is cut off. and F21 parallel resistance R2□
/R, but after cutting the fuse, it becomes a resistance region of only resistance ■12, that is, R21, and by cutting the fuse, (
t+V resistance increases by 1 by R21""21/Rf),
Similarly, in the parallel circuit part of resistor R2□ and polysilicon heater F2□ (R22, 1, 122Z ROll
(31 of resistor R23 and polysilicon fuse F'23
In the 1-column circuit part, the resistance fi'11 is added by J177 by (R23-R23//Rρ. At this time, the weight of these resistances (+) γ1 + 1.i stroke, 2/) is When we set (R2, -R23//R,) = ΔR so that an injury occurs, (■ζ2□-R2□7I,) = 2ΔI, (
R23-R23//R,) -4ΔR, l+1g, l
The resistance values of the resistors R21 to R23 are set so that the resistance is 44+.

Therefore, the resistance value of the variable resistance network 4 consisting of polysilicon fuses F21 to F and resistors R21 to R23 is initially (R2□//R, +R, //R, +I field/R1), When fuse F2□ is cut, ΔR1 fuse F2
When □ is cut, 2ΔR1 fuse F23 is cut 1t'Ji
Then, the 4ΔR resistance increases, so the Hikozu cut 1t'
Depending on the combination of li, 8 values of 11 (, resistance value'
5c, JM can float.

Furthermore, the resistance value of the variable resistance network 5 is (R
24+R,) // (R+Rρ, but F24
After cutting the fuse, it becomes (R25+R,), and by cutting the fuse, it becomes (R25-jR,) - (R24+R,)
The resistance value increases by /(I−R,).

Similarly, after fuse 25 is cut, in the overlapping circuit section of resistor R25 and polysilicon fuse F25, (R240R,)-(R24+R,)//(R25-1-Iζ,)
resistance value increases.

Gain V of the circuit of this example. 1. Since T/v1N&i is given by Offshore, you can plan for a small amount. (
2. Since the variable resistor network 5 is connected in parallel, the increase in resistance caused by cutting the fuse can be increased by 11, which can be fixed monthly in more detail than in series Q'1. Rough adjustment can be made using the resistor ■γ14, and precise adjustment can be made by making fine adjustments using the variable resistance network 5V.

In the circuit of this embodiment, the gain can be adjusted in 24 steps as shown in Table 2 by changing the resistance values of the two variable resistance networks 4.5.

R, 6=(R,, /R, +R2□/几, + 11.
,,//R,.

R2, = (R24 10 liters, )/(R2, 10 liters t)
Jl, 2s=TL, +几, , 11.2. =I+,,
4-M1. .

In addition, if you want to fine=Ira*, polysiliniJU(
: Resistance R, □~R25 is the resistance of polysilicon fuse (
By making it a sufficiently large value compared to 1f,+nt and eliminating the shadow of the polysilicon fuse, V can easily be reduced to 11'z. That is, a series tangent; type “
11 Variable resistance I71. It is possible to greatly increase the gain with the network 4 and reduce the gain ?4I by a small amount with the parallel connected type

In this embodiment, both the resistor and the fuse serving as its short-circuit release means are formed of polysilicon for the following reason.

As mentioned above, the gain of a circuit is expressed as the ratio of two resistance values (formula (
1) 2 (refer to equation (3)). Therefore, if the resistor and fuse are made of the same material, polysilicon, even if the resistance value of the resistor and the resistance value of the fuse itself vary due to manufacturing or ambient temperature, etc. This is because even if fluctuations occur, these fluctuations remain the same, so the value of the ratio of resistance values does not change.

In this way, the gain of the circuit can be kept constant.

FIG. 3 is a circuit diagram showing another embodiment of the present invention, which is a circuit 1f11 that uses five polysilicon fuses and is capable of 32-step gain adjustment.

F31 to F35 each indicate a polysilicon fuse,
R30'' R351R40 is a resistor formed by a polysilicon resistor, and these resistances (ii7, 1-~Ras y R40, respectively). 6 is a resistor.
Atsushi 1 increase, 1 □° nbu.

Similar to the circuit of the embodiment shown in FIG. 2 described above, fJ′I←1
Although it has a parallel connection type
A fixed resistor R40 is connected in parallel to I+'i 8,
In addition, (fixed resistor It3o is connected to the 11-column connected variable resistor network 7)
The point where γ is connected in series is rising. Gain V by inserting resistor I-. jill' the UT/VIN to 32 levels
1j 41B becomes uI function, and by inserting resistor R30, the profit before 7use disconnection? ! 1F+! can be set freely.

In addition, the resistance value change due to cutting of the polysilicon fuse of the 111i'J variable resistor network 7 is weighted by fl, 2, and 2.2, respectively, and the parallel-connected variable resistor 411 and the resistance value j
Resistance (f111) due to polysilicon heat cutting of 8
The change h; is 2, respectively in combination with the resistor R4o.
If the weighting is 2, then the resistance value changes by the series tangent thread) 1 type good resistance network 7 increases the strength of ΔR by 1, the step is 8 steps, and the resistance by the parallel connected variable resistance network 8 and resistor R40. As shown in Table 3, a total of 32 gain adjustments can be made by combining the value changes in 4 steps in decreasing steps of ΔR/4.

Table 3 Table 3 (Continued) R86=(几, □/R,, + R, 32/R, Jubon,
3/Rρ.

几、7=几、. //CR, 34+几, )// (R,
35+几,)R38=R40/(R,3!l+R
,,), 1-=R,/(+13.+n,,) In the embodiments described above, polysilicon resistors and polysilicon resistors forming the series-connected variable resistance network and the parallel-connected uJ variable resistance network・Fuyuse fibrillation 3 each
2 VCs in a row”! Although I am limited to this moment, in general,
71 in series, the number of resistors and fuses forming the type variable resistance network is M (an integer of I'vlt), and the number of resistors and fuses forming the type variable resistance network is N (an integral number of N). Then, there are (M+N) polysilicon fuses and (M+N
2MX (
2N-]) stage (2X (2-1) in the embodiment of FIG.
=24),.

CM+N) or 2 steps (Ic+:2 in the example of FIG.
=32) gain adjustment is possible. Moreover, much more precise adjustment can be made than in the prior art. By doing so, it is possible to obtain a gain adjustment circuit of 4" and 1-roller type, which improves the yield of the device and also allows fine adjustment without being affected by manufacturing conditions since the adjustment is performed by the resistance ratio.

Further, although the explanation so far has been made regarding the case where a polysilicon resistor is used as the resistor and a polysilicon fuse is used as the short-circuit release means, the circuit configuration of the present invention is not limited to this.

For example, it is clear that the same effect can be achieved by using a diffused resistor as the resistor and an analog switch consisting of a transistor (bipolar type or insulated gate field effect type) formed using the same diffusion technology as the shorting/opening means. It is. In this case, the above-mentioned disconnection of the fuse can be handled by opening and closing the switch, so unlike a fuse, once it is disconnected, it is impossible to re-adjust it, but you can repeat the adjustment as many times as you like. (Two-dimensional harmony becomes possible.

As explained in detail above, according to the circuit of the invention, since it has the above-mentioned configuration, ,t'll(υ increase or gain decrease is +1'+It, I'+T,
Since it can be adjusted over multiple stages of 1ψr, the gain of the circuit can be adjusted to f:Ii trace i, which improves the yield of the device. The whole circuit can be turned on and its effect is dog.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example, FIG. 2 is a circuit diagram of an actual example of the present invention, and FIG. 3 is a circuit diagram of another example of the present invention. 1.3.6... Act q, amplifier, 2,4.7...
...Inner row connection type variable resistance network, 5, 8...Parallel connection type iiJ'? Resistance network, R101Rl, ~”131
rt2. ~"Z'l 1R30~"351R40...
...Polysilicon resistor, F□1 to F13. F2, ~
F25. F3□～F35・・・Polysilicon・1
-Us.

Claims (5)

[Claims] (1) It consists of a resistor network in which a plurality of resistors having a short-circuiting/opening means for shorting/opening both ends are connected in series, and the change in resistance value h1 when the short-circuiting/[4f9 releasing means is short-circuited or opened] is binary. Weighted series continuation n]
The variable resistor 11.1 is made up of a resistor network in which several resistors connected in series with the above-mentioned short-circuiting/opening means are connected in parallel, and the resistance 1 ( A parallel-connected variable resistor network in which the change h+ of 1f is determined by the HT constant weight, and the output signal are connected directly to the
Variable resistor 1)) Resistance-divided by the parallel-connected variable resistor 1) and input to the inverting input terminal If
Increase 1i: q'! jTi! Profit q++ starvation circuit with l. (2) Both ends of the series-connected variable resistance wire 1 are shorted (t))
AI:
1ltl, gain adjustment circuit. (3) The parallel-connected variable resistor network includes a resistor that is not connected in one white column to the pre-distribution circuit/opening means. , (gain 1iI7.l rectifier circuit described in Section 21. (4) The resistor is made of a polysilicon resistor, and the shorting/opening means is made of a polysilicon resistor.
Section 2) or Section (3) JJ! Pfl on 1: 4iQ's interest is down! ! 1 circuit. (5) The resistor is a diffused resistor, and 11. j connection・
Does the opening means consist of a transistor or an analog switch? Characteristics: 4'l'H
f1 search) between (1) J-jI Arui l"l:
) term arui) -, l', 'A't (31, 'jr1
;'iii1i;4 II) Gain adjustment circuit.