e 1" id="Figure 1" target="_self">Figure 10. Output current vs output voltage variation of proposed V-I converter.
From AC characteristic, we note an improvement of the gain (Av). Its maximum value is 73 dB but it is 80.2 dB for the proposed version 1 of V-I converter. The bandwidth responses for different values of resistance are presented in Figure 11.
From Figure 12, we present a current error of V-I converter for different values of resistance Rout. On the one hand, the variation of Vin from −0.9 V to 0 V give the same characteristic of error for different values of resistance (Rout = 100 Ω, Rout = 1 KΩ, Rout = 5 KΩ). On the other hand for the maximum current error of 0.35%, Vin is lower than −0.95 V.
5. Application of V-I Converter in Two-Stage Operational Amplifier
Voltage to current V-I converter becomes the most interesting element of interface measurement in the field of mixed signal systems .
The most important parameters to determine high performance of current V-I converters are:
• High linear range.
• Large bandwidth and gain.
Because the large bandwidth and gain of the proposed version 1 of V-I converter, it is possible to use this approach for Operational amplifier [9,10]. The Figure 13 shows a practical implementation of the two-stage Operational amplifier.
The simulated output frequency response of our application is shown in Figure 14. The bode diagram gives an open loop gain of 60 dB with a large GBW of 82 MHz, a 97 KHz of cut-off frequency and a phase margin of 62˚. We note that the input current passes through M8 using for polarisation is equal to 10 µA and this corresponds to an input voltage Vin of −1 V.
Figure 11. Frequency response of proposed V-I converter
Figure 12. Current error of V-I converter.
Figure 13. Proposed two-stage operational amplifier with proposed version 1 of V-I converter.
Figure 14. Frequency response of proposed V-I converter.
Current mirror play an important role in analog circuits used for V-I converter. This work presents two novels design of V-I converter. The version 1 of V-I converter is implemented in Two-Stage Operational Amplifier. However the version 2 gives high output impedance. The use of version 1 due to its large bandwidth of 750 MHz and gain of 80.2 dB. Simulations results of application of V-I converter in two-stage operational amplifier indicated that phase margin is 62˚ to ensure a good stability, gain of 60 dB for ±1.5 V, and GBW of 82 MHz.