IL300 www.vishay.com Vishay Semiconductors Table 1. Gives the value of R5 given the production K3 bin. TABLE 1 - R5 SELECTIONK3R5 RESISTORBINMIN.MAX.TYP.1 % k A 0.560 0.623 0.59 51.1 B 0.623 0.693 0.66 45.3 C 0.693 0.769 0.73 41.2 D 0.769 0.855 0.81 37.4 E 0.855 0.950 0.93 32.4 F 0.950 1.056 1 30 G 1.056 1.175 1.11 27 H 1.175 1.304 1.24 24 I 1.304 1.449 1.37 22 J 1.449 1.610 1.53 19.4 The last step in the design is selecting the LED current limiting resistor (R4). The output of the operational amplifier 3.75 is targeted to be 50 % of the V V = 14.4 mV + 0.6036 x V CC, or 2.5 V. With an LED out in 3.50 quiescent current of 12 mA the typical LED (V LM 201 T = 25 °C F) is 1.3 V. a Given this and the operational output voltage, R4 can be 3.25 calculated. V - V 2.5 V - 1.3 V 3.00 R4 opamp F = ---------------- = ----------------- = 100 I 12 mA Fq 2.75 - Output Voltage (V) out The circuit was constructed with an LM201 differential V 2.50 operational amplifier using the resistors selected. The amplifier was compensated with a 100 pF capacitor 2.25 connected between pins 1 and 8. 4.0 4.5 5.0 5.5 6.0 iil300_19 The DC transfer characteristics are shown in figure 17. The amplifier was designed to have a gain of 0.6 and was Fig. 14 - Transfer Gain measured to be 0.6036. Greater accuracy can be achieved by adding a balancing circuit, and potentiometer in the input divider, or at R5. The circuit shows exceptionally good gain 0.025 linearity with an RMS error of only 0.0133 % over the input 0.020 voltage range of 4 V to 6 V in a servo mode; see figure 15. LM201 0.015 0.010 0.005 0.000 Linearity Error (%) - 0.005 - 0.010 - 0.015 4.0 4.5 5.0 5.5 6.0 iil300_20 V - Input Voltage (V) in Fig. 15 - Linearity Error vs. Input Voltage The AC characteristics are also quite impressive offering a -3 dB bandwidth of 100 kHz, with a -45° phase shift at 80 kHz as shown in figure 16. Rev. 1.8, 02-Jun-14 8 Document Number: 83622 For technical questions, contact: optocoupleranswers@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000