A hybrid integrated operational amplifier offset performance adjustment method and adjustment structure

Abstract

A hybrid integrated operational amplifier offset performance adjustment method and adjustment structure, belonging to the field of integrated circuits, comprises one or more operational amplifiers, each including two offset voltage adjustment terminals. The two offset voltage adjustment terminals of the first-stage operational amplifier are connected to a adjustment resistor network. An output offset voltage expression is derived based on the circuit structure of the hybrid integrated operational amplifier. In this output offset voltage expression, the output offset voltage is assumed to be zero. Except for the adjustment resistor used to adjust the output offset voltage, all other electrical parameters are known to have fixed values. The adjustment resistor value is calculated from this. Laser adjustment is then used to adjust the adjustment resistor to a set precision, thereby achieving offset performance adjustment for the hybrid integrated operational amplifier. This method solves the problems of blind adjustment, low adjustment efficiency, low product yield, and large space requirements. It is widely used in miniaturized, high-precision small-signal amplification circuits.

Description

Technical Field

[0001] The present invention belongs to the field of integrated circuits, and further relates to the field of hybrid integrated circuits, and in particular to a method for adjusting the offset performance of a hybrid integrated operational amplifier and an adjustment structure thereof. Background Art

[0002] In a multi-stage amplifier circuit composed of operational amplifiers, the output offset is large due to the high system amplification factor, which does not meet the use requirements.

[0003] Typically, a single-channel operational amplifier has seven pins, including a positive input terminal, a negative input terminal, an output terminal, a power supply terminal, a ground terminal, and two trim terminals, namely, a positive input terminal IN+, a negative input terminal IN-, an output terminal Vout1, a ground terminal GND, power supply terminals VCC and VSS, and trim terminals T11 and T12. Figure 1 As shown in Figure 1, the input terminal Vin of the system is connected to the negative input terminal of operational amplifier U1 through resistor R1. Resistor R1 is also connected to one end of resistor R2, and the other end of resistor R2 is connected to the output terminal Vout1 of operational amplifier U1. Thus, operational amplifier U1, R1, and R2 form negative feedback. When the system has only one stage, the output voltage Vout1 of the amplifier formed by operational amplifier U1 can be expressed as follows:

[0004] Vout1=Vin*A1+Vos1*A1

[0005] In the above formula, A1 represents the closed-loop DC voltage amplification factor of the first-stage operational amplifier U1, and Vos1 represents the input offset voltage of the first-stage operational amplifier U1.

[0006] When the input signal Vin is zero, the output voltage Vout1 is the output offset voltage Voos1 of the closed-loop system formed by the operational amplifier U1, and the expression is as follows:

[0007] Voos1=Vos1*A1

[0008] By analogy, when the system consists of two or more stages, the output offset voltage of the entire system is Voosn, which is expressed as follows:

[0009] Voosn=Vos1*A1*A2*...*An+Vos2*A2*A3*...*An+...+Vosn*An

[0010] From this, it can be seen that achieving output offset parameters that meet design requirements is crucial. The first-stage output offset contributes most significantly to the system. Theoretically, by introducing appropriate resistors R1C and R2C at the trim terminals Tn1 and Tn2 of each stage, the output offset voltage can be adjusted, thereby achieving offset parameters that meet operational requirements. Generally, simply trimming the two trim terminals of the first stage will meet the requirements. Among the many parameters of a hybrid integrated circuit operational amplifier, the output offset voltage is a key parameter for evaluating the overall performance of the entire amplifier, with the lower the output offset voltage, the better.

[0011] The circuit connection of the operational amplifier trimming terminals Tn1 and Tn2 is as follows: Figure 2 shown.

[0012] The traditional trimming method is to complete the corresponding soldering of the entire operational amplifier on a PCB, test the output offset parameters by powering on, and then replace the trimming resistors R1c and R2c at the trimming terminals Tn1 and Tn2 of the operational amplifier back and forth to make the output offset of the entire operational amplifier meet the system application requirements.

[0013] While this method can be used when space is not limited, it is time-consuming. The selection of R1c and R2c is arbitrary, and an external rheostat is generally required to determine the trimming resistance value. Furthermore, since the resistor values are limited to nominal values, their application is somewhat restricted.

[0014] To meet the demands of equipment miniaturization, integration, and multifunctionality, and to improve equipment reliability, most complete systems, including the electronic components they use, need to be miniaturized simultaneously. To this end, several electronic components are integrated together through hybrid integration to create a new, miniaturized device that meets system requirements. For example, low-offset operational amplifiers are being replaced by single-packaged devices instead of traditional, separately packaged components. This creates a problem: due to the limited internal trimming methods and complex processes of hybrid integrated circuits, most components are directly integrated together without prior trimming, resulting in a low product yield.

[0015] In view of this, the present invention is proposed. Summary of the Invention

[0016] The technical problem to be solved by the present invention is to solve the problems of blindness, low adjustment efficiency, low product yield and large space occupation in existing adjustment methods.

[0017] To this end, the present invention provides a method for adjusting the offset performance of a hybrid integrated operational amplifier. The hybrid integrated operational amplifier includes one or more operational amplifiers, each including two offset voltage adjustment terminals. The two offset voltage adjustment terminals of the first-stage operational amplifier are respectively connected to an adjustment resistor network. An output offset voltage expression is derived based on the circuit structure of the hybrid integrated operational amplifier. In the output offset voltage expression, the output offset voltage is assumed to be zero. Except for the adjustment resistor used to adjust the output offset voltage, all other electrical parameters are known to be constant values, thereby calculating the value of the adjustment resistor. The operational amplifier is integrated using semiconductor chip technology and then hybrid-integrated with the adjustment resistor network. The adjustment resistor network is then adjusted using a laser adjustment method to achieve a set adjustment resistor value, thereby adjusting the offset performance of the hybrid integrated operational amplifier.

[0018] A hybrid integrated operational amplifier offset performance adjustment method and corresponding adjustment structure, such as Figure 1 、 Figure 2 shown.

[0019] The system includes operational amplifiers U1, U2, ..., Un, and resistors R1, R2, ..., R3n. Each operational amplifier has two trimming terminals T11, T12, ..., Tn1, Tn2, where n is a natural number greater than or equal to 1.

[0020] One end of the resistor R1 is connected to the input terminal Vin, and the other end is connected to the negative phase input terminal IN- of the operational amplifier U1. It is also connected to one end of the resistor R2, the other end of which is connected to the output terminal Vout1 of the operational amplifier U1. It is also connected to one end of the resistor R4, the other end of which is connected to the negative phase input terminal IN- of the operational amplifier U2. It is also connected to one end of the resistor R5, the other end of which is connected to the output terminal Vout2 of the operational amplifier U2. Similarly, one end of the resistor R3n-2 (the "-" in the resistor number 3n-2 represents a minus sign, the same below) is connected to the output terminal of the previous operational amplifier, and the other end is connected to the negative phase input terminal IN- of the operational amplifier Un. It is also connected to one end of the resistor R3n-1, the other end of the resistor R3n-1 is connected to the output terminal Voutn of the operational amplifier Un, and finally outputted by Voutn.

[0021] The operational amplifier is a differential input amplifier. Its trim terminal Tn1 is connected to one end of an internal chip resistor R1A and one end of a resistor R2A. The other end of resistor R2A is connected to the power supply VCC, and the other end of resistor R1A is connected to the differential input stage output terminal VoA of the operational amplifier. Trim terminal Tn2 is connected to one end of an internal chip resistor R1B and one end of resistor R2B. The other end of resistor R2B is connected to the power supply VCC, and the other end of resistor R1B is connected to the differential input stage output terminal VoB of the operational amplifier. R1A, R2A, R1B, and R2B are internal resistors of the operational amplifier.

[0022] When performing offset performance adjustment on an operational amplifier system, the adjustment method includes connecting one end of adjustment terminal Tn1 to one end of R1A and one end of R2A, and connecting the other end of Tn1 to one end of an external adjustment resistor R1c, which is connected to a power supply VCC. Connecting one end of adjustment terminal Tn2 to one end of R1B and one end of resistor R2B, and connecting the other end of Tn2 to one end of an external adjustment resistor R2c, which is connected to a power supply VCC. The external adjustment resistor R2c is set as a fixed resistor, and the external adjustment resistor R1c is set as an adjustable resistor. The output offset voltage expression of the operational amplifier is used to calculate the resistance value of the external adjustment resistor R1c that equals zero output offset voltage. Laser adjustment is then used to adjust the external adjustment resistor R1c to a predetermined resistance value, thereby achieving offset performance adjustment for the operational amplifier.

[0023] The resistors R1, R2, ..., R3n are all metal film resistors, and the trimming resistors R1c and R2c are metal film resistor array chips.

[0024] The operational amplifiers U1 , U2 , . . . , Un, the resistors R1 , R2 , . . . , R3n, and the trimming resistors R1c and R2c are integrated into one package in a hybrid integration manner.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] 1. Without changing the device package, there is no need to connect an external sliding resistor to determine the trimming resistor value, and there is no need to consider whether the trimming resistor value is the nominal value.

[0027] 2. No need to perform multiple adjustments. Just test the output offset parameters of the operational amplifier circuit by powering on, calculate the trimming resistor value, obtain high-precision trimming resistor value through laser trimming, and complete the corresponding connection inside the device.

[0028] 3. The adjustment method is simple and flexible, and is not restricted by the resistance value, which effectively improves the adjustment efficiency and reduces the device cost.

[0029] 4. The output offset parameter of the operational amplifier circuit can be controlled to less than or equal to plus or minus 5mV under 1500 times conditions, which greatly improves the parameters of the circuit.

[0030] 5. It can be widely used in miniaturized, high-precision small signal amplifier circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the principle of a multi-stage operational amplifier circuit.

[0032] Figure 2 This is a schematic diagram of the internal and external connection principles of the trimming resistor.

[0033] Figure 3 This is a schematic diagram of the two-stage operational amplifier circuit principle. DETAILED DESCRIPTION

[0034] Take the FH2120 low offset operational amplifier of Guizhou Zhenhua Fengguang Semiconductor Co., Ltd. as an example. Figure 3 As shown, the specific embodiments are described in detail as follows:

[0035] The resistance calculation expression of R1c is:

[0036] Vout2=It*(R2B / / R2c-R2A / / R1c)*As+Vav (1)

[0037] In expression (1), the values of It, R2B, R2A, and R2c are fixed and set according to the specific circuit and parameter requirements. Vav is the amplifier circuit correction value, calculated by power-on testing before the product is sealed, and As is the circuit amplification factor. To achieve zero output offset voltage Vout2, the product needs to be trimmed for offset performance. By setting Vout2 equal to zero in expression (1), and knowing all parameters except R1c, the trimming resistor value can be calculated.

[0038] In a given package, operational amplifiers U1 (OP77) and U2 (OP77) are bonded together using a hybrid integrated circuit method. Resistors R1 (1KΩ), R2 (30KΩ), R3 (0.97KΩ), R4 (2KΩ), R5 (100KΩ), R6 (1.96KΩ), and R1c are bonded together. Resistor R2c is a fixed 10KΩ. The corresponding electrical connections are made according to the circuit schematic.

[0039] In expression (1): It is 0.000000615, R2B is 15.405KΩ, R2A is 15.405KΩ, R2c is 10KΩ, and As is 1500 times. Let Vout2 in expression (1) be zero. Except for the resistance of R1c, all other parameters are known, and the resistance of the trimmed resistor can be calculated. Then, laser trimming is used to obtain the high-precision resistance of R1c, according to Figure 3 The circuit in the dotted box is electrically connected on the substrate inside the package, and then the cover is completed and the product is trimmed. After trimming, the output offset voltage of the amplifier can be controlled within 5mV.

[0040] The above-mentioned trimming method can effectively solve the problems caused by low trimming efficiency, non-standard trimming resistor values, and low product yield, and can greatly improve product production efficiency and quality consistency.

[0041] Finally, it should be noted that the above embodiments are merely examples for clarity of explanation. The present invention includes, but is not limited to, these embodiments. An exhaustive list of all possible implementations is not necessary and cannot be provided here. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. Any implementation that meets the requirements of the present invention is within its scope.

Claims

1. A method for adjusting the offset performance of a hybrid integrated operational amplifier, characterized by: The hybrid integrated operational amplifier includes one or more operational amplifiers, each including two offset voltage trimming terminals; the two offset voltage trimming terminals of the first-stage operational amplifier are respectively connected to a trimming resistor network; an output offset voltage expression is derived based on the circuit structure of the hybrid integrated operational amplifier, wherein the output offset voltage is assumed to be zero, and the values of the trimming resistors are calculated based on the known values of the remaining electrical parameters except for the trimming resistors used to adjust the output offset voltage; the operational amplifier is integrated using semiconductor chip technology and then hybrid-integrated with the trimming resistor network; the trimming resistor network is then trimmed using a laser trimming method to achieve a trimming resistor value with a set accuracy, thereby achieving trimming of the offset performance of the hybrid integrated operational amplifier; The adjustment structure of the adjustment method includes: Operational amplifiers U1, U2, ..., Un, resistors R1, R2, ..., R3n, each of the operational amplifiers having two trimming terminals T11, T12, ..., Tn1, Tn2, where n is a natural number greater than or equal to 1; One end of the resistor R1 is connected to the input terminal Vin, and the other end is connected to the negative phase input terminal IN- of the operational amplifier U1, and is also connected to one end of the resistor R2. The other end of the resistor R2 is connected to the output terminal Vout1 of the operational amplifier U1, and is also connected to one end of the resistor R4. The other end of the resistor R4 is connected to the negative phase input terminal IN- of the operational amplifier U2, and is also connected to one end of the resistor R5. The other end of the resistor R5 is connected to the output terminal Vout2 of the operational amplifier U2; and so on. One end of the resistor R3n-2 is connected to the output terminal of the previous operational amplifier, and the other end is connected to the negative phase input terminal IN- of the operational amplifier Un, and is also connected to one end of the resistor R3n-1. The other end of the resistor R3n-1 is connected to the output terminal Voutn of the operational amplifier Un, and is finally output by Voutn; The operational amplifier is a differential input amplifier, wherein the trimming terminal Tn1 is connected to one end of the chip internal resistor R1A and one end of the resistor R2A; the other end of the resistor R2A is connected to the power supply VCC, and the other end of the resistor R1A is connected to the differential input stage output terminal VoA of the operational amplifier; the trimming terminal Tn2 is connected to one end of the chip internal resistor R1B and one end of the resistor R2B; the other end of the resistor R2B is connected to the power supply VCC, and the other end of the resistor R1B is connected to the differential input stage output terminal VoB of the operational amplifier; wherein R1A, R2A, R1B, and R2B are internal resistors of the operational amplifier; One end of the trimming terminal Tn1 is connected to one end of R1A and one end of R2A, and the other end of Tn1 is connected to one end of the external trimming resistor R1c, and the other end of the external trimming resistor R1c is connected to the power supply VCC; one end of the trimming terminal Tn2 is connected to one end of R1B and one end of the resistor R2B, and the other end of Tn2 is connected to one end of the external trimming resistor R2c, and the other end of the external trimming resistor R2c is connected to the power supply VCC.

2. The method for adjusting offset performance of a hybrid integrated operational amplifier according to claim 1, wherein: The resistors R1, R2, ..., R3n are metal film resistors, and the trimming resistors R1c and R2c are metal film resistor array chips; the operational amplifiers U1, U2, ..., Un, the resistors R1, R2, ..., R3n, and the trimming resistors R1c and R2c are integrated into a package through hybrid integration.

3. The method for adjusting offset performance of a hybrid integrated operational amplifier according to claim 1, wherein: The external trimming resistor R2c is a fixed resistor, and the external trimming resistor R1c is an adjustable resistor. The output offset voltage expression of the operational amplifier is used to calculate the resistance value of the external trimming resistor R1c at which the output offset voltage is equal to zero. Then, the external trimming resistor R1c is trimmed using a laser trimming method to achieve the set precision of the external trimming resistor R1c resistance value, thereby achieving the adjustment of the offset performance of the operational amplifier.

4. The method for adjusting offset performance of a hybrid integrated operational amplifier according to claim 1, wherein: Said n is equal to 2.

5. The method for adjusting offset performance of a hybrid integrated operational amplifier according to claim 4, wherein: The resistance calculation expression of the external trimming resistor R1c is: Vout2=It·(R2B / / R2c-R2A / / R1c)·As+Vav; The values of It, R2B, R2A and R2c are fixed values and are set according to the specific circuit and parameter requirements; Vav is the correction value of the amplifier circuit, which is calculated through power-on testing before the product is capped; As is the circuit amplification factor; and R1c is an adjustable resistor.

6. The method for adjusting offset performance of a hybrid integrated operational amplifier according to claim 5, wherein: U1 and U2 are OP77, R1=1KΩ, R2=30KΩ, R3=0.97KΩ, R4=2KΩ, R5=100KΩ, R6=1.96KΩ, R2 c=10KΩ, It=0.000000615, R2B=15.405KΩ, R2A=15.405KΩ, R2c=10KΩ, As=1500.

7. The offset performance adjustment structure of the hybrid integrated operational amplifier according to claim 6, wherein: The output offset voltage is within 5mV.

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