Shadow resistance-to-frequency and resistance-to-time converter

A method for assembling a resistance-to-frequency, resistance-to-time converter, comprising:

• connecting a non-inverting input Y1 to an internal output Z1 of a first current feedback operational amplifier (CFOA), the first CFOA having an inverting input X1, an internal output W1 and an external output V0;
• connecting a resistor R2 between a ground terminal and the non-inverting input Y1;
• connecting the resistor R2 to a non-inverting input Y2 of a second CFOA, the second CFOA having an inverting input X2, an internal output Z2, an internal output W2 and an external output Vtr;
• connecting the resistor R2 between the ground terminal and the non-inverting input Y2;
• connecting a resistor R3 between the ground terminal and the inverting input X2;
• connecting a capacitor C between the ground terminal and the internal output Z2;
• connecting the external output Vtr to a non-inverting input Y3 of a third CFOA having an inverting input X3, an internal output Z3, an internal output W3 and an external output V1;
• connecting a resistor R1 between the external output V1 and the inverting input X1,
• connecting a variable resistor RT between the ground terminal and the inverting input X3;
• connecting a variable resistor RF between the ground terminal and the internal output Z3;
• connecting a positive DC voltage to a positive bias terminal of each CFOA;
• and
• connecting a negative DC voltage to a negative bias terminal of each CFOA.

The method of operating a resistance-to-frequency, resistance-to-time converter, comprising:

• generating a square wave having a positive amplitude VSAT+ and a negative amplitude VSAT− at an external output V0 of a circuit comprising:
• a first current feedback operational amplifier (CFOA) having an inverting input X1, a non-inverting input Y1, an internal output Z1, an internal output W1 and the external output V0, wherein the non-inverting input Y1 is connected to the internal output Z1;
• a second CFOA having an inverting input X2, a non-inverting input Y2, an internal output Z2, an internal output W2 and an external output Vtr, wherein the non-inverting input Y2 is connected to a resistor R2 and to the non-inverting input Y1, the inverting input X2 is connected to a resistor R3, the internal output Z2 is connected to a capacitor C, wherein the resistor R2, the resistor R3 and the capacitor C are connected to a ground terminal;
• and
• a third CFOA having an inverting input X3, a non-inverting input Y3, an internal output Z3, an internal output W3 and an external output V1, wherein the external output V1 is connected by a resistor R1 to the inverting input X1, wherein the inverting input X3 is connected to a variable resistor RT, wherein the internal output Z3 is connected to a variable resistor RF, wherein the non-inverting input Y3 is connected to the external output Vtr, wherein the non-inverting input Y3 is connected to the external output Vtr, voltage saturating each CFOA;
• selecting a period T of the square wave by varying a magnitude of the variable resistor RT and a magnitude of the variable resistor RF;
• and
• selecting a frequency of oscillation f of the square wave by varying the magnitude of the variable resistor RF and the magnitude of the variable resistor RT.