input end zero circuit

Published:2011/5/8 2:51:00 Author:John | Keyword: input end zero circuit | From:SeekIC

Figure (a) is a relatively simple circuit, which uses the input resistors R1 and feedback resistor R2 as one part of the attenuation, together with the resistor R3 at the inverting input in order to generate a variable offset voltage. The voltage is divied from the R3 and R1 ∥ R2. ± 15V power supply is connected at both ends of the potentiometer R4. And the partial pressure ratio is about 1000 / 1. So the offset voltage can be ranged within ± 15mV . For Figure (a), the general formul for calculating adjustment range of the offset voltage is: offset voltage range = ± VD • [(R1 ∥ R2) / R3] (± VD = ± 15V) When there are multiple input signals on the the reverse side, the offset voltage ranges just as shown in virtual display line of Figure (a). multiple input offset voltage range = ± VD [(R1 ∥ R2 ∥ Rl ') / R3] (± VD = ± l5V) Comparing the above two equations, the former one is clearly with a wider voltage range of adjustment voltage. To increase the voltage adjustment range of the latter one, it is suggested to appropriately change the size of resistor R5. Figure (b) shows that this circuit has a wide range of applications, because the adjustment voltage has nothing to do with feedback components. And adjustment voltage is set in both input ends, avoiding the winning stream signaling pathways. In this circuit, R3 and R5 of the resistance (100kΩ, 100Ω) form 1000 / I of the voltage divider. And R5 will get adjustment range of ± 15mV offset voltage at both ends. When R3 and R5 are set at other values, adjustment range of offset voltage can be determined by the following formula: offset voltage adjustment range = ± VD • (R5/R3) (± VD = ± l5V) There is few requirements for resistance of resistors R3 and R5. In fact, it is better to choose the resistance of resistor R5 below 1kΩ.



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