TWI241765B - Variable gain amplifying circuit - Google Patents

Abstract

The present invention discloses a variable gain amplifying circuit which applies a resistor ladder to obtain a more accurate gain. The amplifying circuit includes an input, an operational amplifier (op-amp), a resistor unit and a feedback resistor. The feedback resistor is coupled between an output and an inverting input of the op-amp, and the resistor unit is coupled between the input of the amplifying circuit and the inverting input of the op-amp. The resistor unit includes at least a resistor ladder. The resistor unit further includes a switch unit for switching on/off the resistor ladder. The present invention can also be applied to a differential amplifying circuit for more accurate gain adjustment.

Description

1241765 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a variable gain amplifier circuit, especially a variable gain amplifier circuit with a ladder resistor structure. 〃 [Previous technology] In today's circuit design, it is often necessary to provide a high-precision signal amplification function. For example, in common wireless communication modulation mechanisms, both phase modulation and frequency modulation use I / Q signals. However, as long as the amplitude of the I / Q signal is slightly mismatched, it will destroy the signal constellation diagram and increase the bit error rate (bER) of the communication system. Therefore, it is necessary to use an amplifier with high precision gain to accurately control the amplitude of the / Q signal. Generally, the gain drift of the open-loop amplifier is quite large, so it does not meet the requirements of the precise gain of the surface; and the commonly used closed-loop amplifier is not easy to accurately control the gain.目-The circuit of a conventional closed-loop amplifier ^ Eight packs of operational amplifier 10, one coupled between the input terminal and the operational amplifier 10, a resistor Ri between the inverting input terminal, and one coupled between the output terminal and the operational amplifier The feedback resistance R v between the inverting input terminals of 10 is the input voltage and the output voltage, respectively. Due to the characteristics of negative feedback and virtual short; (, ;; two: short), the gain value (yt / Vin) of the amplifier circuit in Figure 1 can be deduced to be h / h, by adjusting the resistance values of Rl and dagger To get the required chirp gain. However, if you want to use the circuit in Figure 1 to obtain a high-precision gain, such as 1.001 times, the difference between the resistance value of & and the heart is quite large (such as & μ k ohm, I ^ lk + l ohm), It is easy to affect the accuracy of the gain because of a slight error compared to the resistance value of 1 1241765 V. Description of the invention (2). Especially when implemented on integrated circuit (IC), it is not easy to fully grasp such factors as temperature, process, supply voltage drift, etc., and it is even more difficult to achieve such high accuracy. SUMMARY OF THE INVENTION In view of this, an amplifying circuit of the present invention can use a trapezoid to provide a better gain value. Another object of the present invention is to correct the gain mismatch due to temperature and process. In order to achieve the aforementioned purpose, the circuit includes an input terminal and a feedback resistor. The operational amplifier has an input terminal and an output terminal. Between the output terminal and the inverting input terminal, and the input terminal and the inverting of the operational amplifier are a ladder resistor and a control ladder. One and one second resistors block. The differential operational amplifier has a non-inverting output terminal and a non-inverting output terminal of the non-inverting output. The purpose is to propose a variable resistance-increasing architecture for fine-tuning the gain. Due to factors such as supply voltage drift, a variable gain amplifier amplifier, a resistor device, an inverting input terminal, and a grounded positive-phase feedback resistor coupled to the op amp's output resistor device are coupled. Between the input terminals of the amplifier circuit. The resistive device includes at least a switching unit that turns on or off the resistance. Provides a differential gain negative input terminal with a variable gain, a differential operational amplifier, and a first and a second feedback power input, a non-inverting input terminal, and a terminal. The first feedback resistor is coupled between the differential inverting wheels and the second feedback resistor

Page 7 1241765 V. Description of the Invention (3) — The resistor is coupled between the inverting of the differential operational amplifier. The first Xueyang station, such as the company μ, is connected to the positive phase input terminal and the-resistor: between the Jin input terminal and the positive wheel input terminal,: Γ ί ΞΓ; between the positive phase input terminal and the negative wheel input terminal. Each first set includes at least one first-shaped resistor and a first switch that controls whether the resistor is conductive or not. The device includes at least a second ladder resistor and a control that controls whether a second switch unit is conductive or not. Each of the first ladder resistors is [Embodiment] The preferred embodiment of the present invention will be explained in detail in accordance with the drawings. The resistance value has been further improved throughout the month. On the day of this issue, the f series uses a chirp resistor to adjust the power of the closed-loop amplifier circuit in order to achieve a more precise control of the gain. Resistance circuit structure and principle. First, let ’s talk about the moon trapezoidal electricity (that is, the second series of square diagrams, showing the circuit structure diagram of the five-step ladder resistance, "in each stage of the resistance R, V ν The value is electrical resistance 22, 1 " 24, 1 ^ resistance network, and its :, ρ, the ladder resistance of Figure 2 is 5-bit _, the 4-effect circuit of the resistance value can be derived as follows: the resistance 'and, parallel ... , 'Is in series with the resistance dagger 2, the equivalent impedance is 2R. Then the equivalent 221, 22, 24, 26, and 28) each have a node (labeled 201, ground, 261, and 281) and two current paths One of them is coupled to the original value ^ i and the other !! is coupled to the next level node. Figure_Resistance combination of resistance R, ° D for each resistor, but for simplicity, here we will use the electricity page 8 1241765 V. Description of the invention (4) The impedance is then connected in parallel with ‘and so on. So when current! Since the input point V = after '= nodes 281, 261, 241, 221, and 201, the resistance of the two current paths is 2R, so after passing through each node, the current will be equal to ... The amount is shown in the figure. Because the ladder resistor in Figure 2 is too small, it is output after taking it ^. The output current is 1/25, which represents this: the equivalent resistance value of the shape resistor is 25XR. The equivalent resistance of the R-2R resistor network = 1 is 2ηχ r. / Push, η bit π Next, how to implement such a trapezoidal gain amplifier circuit will be described. " 俜 The second of the present invention: a circuit applied to the variable augmentation embodiment of the present inventionΐ One of the better amplifiers of the gain amplifier is a resistor = two = = circuit 3: including the configuration of arithmetic operation and feedback, That is, the operation zooms in qn &. The amplifier circuit 3 is a negative ground point, and the non-inverting input terminal of the feedback lightning R 0, | ^ is connected to the inverting input terminal: electricity = then =; the output terminal of the operational amplifier 30 and the operational amplifier 30; Phase power transmission is transmitted via a resistor. In FIG. 2, the resistance device 32 includes a power amplifier, a power switch 32, and a switch unit 322. Un resistors 321-1 to ㈣ in the resistor network, resistors such as resistor 32b and 1 are 1 bit, and so on. Switch unit 322; control resistor network ...: 32 Bu. Whether it is on or not, it is used to adjust the entire value of 32H. The equivalent resistance of the device 32 can be deduced as shown in Figure III. The description of Figure 2 on the equivalent resistance of the resistor device 32 of 2R is ···

Η Yi Wei If the feedback resistance dagger

The resistance value of m χ R can be deduced to increase the amplification circuit 3 ^ 1 1 • Η--Η-- 23 2r By M a month-> Formula (1-1) or delete, & Zaofan 322 'Can decide whether each item in formula (Η)

The resistor device Λ I precisely adjusts the required gain value. The larger the value of η, which is the achievable 3 (the greater the number of bits in the R-2R resistor network, the greater the accuracy of the amplification signal if V is determined to be deleted). Of course, the formula (Bu 10 For example :, you can directly omit the corresponding R-2R resistor network. The gain value range to be adjusted from Θ to the right is between 1 and 25. Then t 丄 and resistance b The resistance value is set to 2R, and it is judged that the two items 22 and 23 need to be deleted according to the formula ο]). Therefore, the 2-bit and 3-bit resistance network and 321-3 can be omitted. ^ Formula (1-1) If the items in the formula are determined to be retained, without affecting the accuracy of the plastic gain, the R_2R resistor network corresponding to the reserved items can be directly replaced by another equivalent resistance unit to save the potential. The area of the variable gain amplifier circuit.

It is worth noting that the ladder resistors 32b1 to 32bn used in the embodiment of FIG. 3 are not limited to the R-2R resistor network. Anyone who is familiar with this technique can make some modifications and retouches to the structure of this ladder resistor. For example, set the ratio of the resistance on the two current paths of each level in the ladder resistor to other ratios other than 1.2. As long as the final gain of the amplifier circuit can be expressed as

Page 10 V. Description of the invention (6) U, 1) Those who make adjustments to achieve control effects do not depart from the spirit and scope of the present invention. The invention can also be applied to the configuration of a differential amplifier circuit. FIG. 4 is a circuit diagram of a preferred embodiment of the variable gain differential amplifier circuit of the present invention. For example, the differential amplifier circuit 4 includes a differential operational amplifier 40. Each of the differential amplifier circuits 4 is coupled between the ^ phase wheel output and the inverting input terminal, and between the inverting output terminal and the positive phase two input terminal. Feedback resistance h. In addition, the input voltage ^ is sent to the inverting input terminal of the differential operational amplifier 40 through a resistance device 32, and the input voltage vA_ is sent to the 40 f-phase input terminal of the differential operational amplifier 40 through another resistance device 32. It should be noted that in the embodiment of Fig. 4, the equivalent resistance values of the two resistors are the same, and the resistance values of the two feedback resistors and

The resistor device 32 and the feedback resistor R31 used in FIG. 4 are the same as those used in FIG. Equation (1-1) is similar to whether the switching unit 322 in the resistive device 32, or the items in the equation (/) are retained or deleted, and then the adjusted gain value is accurately adjusted. Similarly, the larger the value of η, that is, the larger the number of bits of the resistance network of the resistor device 3 2, the greater the accuracy of the S circuit that can be achieved by the amplifier circuit 4. · The above is a detailed description of the present invention using the preferred embodiments, and is not limited to 1241765 V. Description of the invention (7) The scope of the present invention is made. Anyone who is familiar with such arts can understand that making appropriate changes and adjustments will still not lose the essence of the invention, nor depart from the spirit and scope of the invention. To sum up, the specificity of the implementation of the present invention has already met the requirements of the invention patent stipulated in the Patent Law. I invite your reviewing committee to review it and grant the patent as a prayer.

Page 12 1241765 Brief description of the diagram Figure 1 is a circuit diagram of a conventional closed-loop amplifier. Figure 2 shows the circuit structure of a five-step ladder resistor. FIG. 3 is a circuit diagram of a preferred embodiment of the variable gain amplifier circuit of the present invention. Fig. 4 is a circuit diagram of a preferred embodiment of the variable gain differential amplifier circuit of the present invention. Description of the drawing number of the drawing: 10, 30: Operational amplifier 2 0, 2 2, 2 4, 2 6, 2 8: One-stage ladder resistor 201, 221, 241, 261, 281: Node 3 2: Resistor device 321- 1 ~ 321-n ·· Ladder resistor 3 2 2: Switch unit 40: Differential operational amplifier

Page 13

Claims (1)

1241765 6. Scope of patent application 1. A variable gain amplifier circuit including: an input terminal; an operational amplifier having an inverting input terminal, a non-inverting input terminal connected to a ground point, and an output terminal ; At least one ladder resistor is connected between the inverting input terminal and the input terminal; a switch unit is used to control whether the at least one ladder resistor is conductive; and a feedback resistor is connected to the operational amplifier. Between the output terminal and the inverting input terminal. 2. The amplifying circuit described in item 1 of the scope of patent application, wherein the at least one ladder resistor is an R-2 R resistor network. 3. The amplifying circuit according to item 1 of the scope of patent application, wherein the gain of the amplifying circuit is changed by controlling the switching unit. 4. A variable gain differential amplifier circuit comprising: a positive input terminal and a negative input terminal; a differential operational amplifier having an inverting input terminal, a non-inverting input terminal, an inverting output terminal, and a Non-inverting output terminal; at least one first ladder resistor coupled between the inverting input terminal and the positive input terminal; a first switch unit for controlling whether the at least one first ladder resistor is conducting, at least one first Two ladder resistors, coupled between the positive input terminal and the negative input terminal; Page 14 1241765 — The second switch unit is turned on; used to control whether the at least one second ladder resistor is 1 = hour: resistor 1 is connected between the non-inverting output of the differential operational amplifier and the inverting input terminal; and two feedback resistors are coupled between the inverting output terminal of the differential operational amplifier and the Between non-inverting inputs. 5. The differential amplifier circuit according to item 4 of the scope of patent application, wherein the at least one first ladder resistor is an r_2R resistor network. 6. The differential amplifier circuit according to item 5 of the scope of the patent application, wherein the at least one second ladder resistor is a -2R resistor network. 7. The differential amplifier circuit according to item 4 of the scope of the patent application, wherein the at least one first and the at least one second ladder resistance have the same equivalent resistance value. 8. The differential amplifier circuit described in item 7 of the scope of patent application, wherein the first and second feedback resistors have the same resistance value. 9. The differential amplifier circuit according to item 4 of the scope of patent application, wherein the gain of the differential amplifier circuit is adjusted by controlling the first or the second switching element or both. H A variable gain amplifier network, including: an input terminal; an operational amplifier number, and a / inverting input terminal, coupled to a ground point-normal phase input terminal and output terminal; a switch The resistor device between the inverting input terminal and the input terminal includes: Page 1241765 VI. Patent application scope: a first ladder resistor; a second ladder resistor; and a switch unit, which are respectively coupled to the first and second ladder resistors, and control whether the ladder resistors are conductive; A feedback resistor is coupled between the output terminal of the operational amplifier and the inverting input terminal. 11. The amplifying circuit according to item 10 of the scope of patent application, wherein the ladder resistors are an R-2 R resistor network. 1 2. The amplifier circuit according to item 10 of the scope of patent application, wherein the number of stages of the first ladder resistor and the second ladder resistor are different. 13. The amplifier circuit according to item 10 of the scope of patent application, wherein the gain of the amplifier circuit is changed by controlling the switch unit. Page 16