Aso, Shalika
The circuit was finalised to be made for EOM. The simulation was done in LTspice. We almost have all components in elec shop.
It was taken care that impedance is matched between source(moku) and circuit using OpaAmp. The OP27 planned to be used should have output current max as 30mA.
The EOM will have
1. Moku will provide 0.1 V
2. Resonant frequency of 979.2 KHz.
3. Gain is around 3.01k
4. Output current of Op27 is 24.2 mA
5. Matched imepdance is around 49.5 ohm.
Fig 1 shows the circuit diagram and Fig 2 shows the transfer function plot.
The datasheet of OP27 for reference.
The Vpi, half wave voltage for the EOM is defined by the equation
V_{pi} = 0.361 * lambda - 23.844 = 0.361 * 1064 - 23.844 = 360.26 V (considering crystal with 14pF capacitane). The one we have says a capacitance of 12pF.
(where lambda is in nm)
I tuned the circuit a bit more to obtain the gain of 7.397k with Moku supplying a 0.05V. So, with the updated circuit we will have
1. 0.05*7.397k = 369.8 V
2. Impedance of 48.9 ohm
3. OpAmp current of 11 mA.
4. Resonant frequency of 0.39MHz
I have updated the circuit diagram and transfer function.
PS: Moku can provide minimum of 1mVp-p using waveform generator function.
I can use a feedback resistance of 1.1k instead of 1.07k, since 1.1k is readily available. Also, the inductors measure about 6.4mH(using multimeter), instead of 6.8mH. In series they will be 12.8mH instead of 13.6m in the deisgn. This shifts the resonant frequency by 18kHz, but doesn't change the gain or the current properties of the circuit too much. So, even if the components will not be perfect we will not overshoot the 20mA limit of the opAmp current at the output.
The OpAmp in elec shop is Op27G / OP27 whose max current is 20mA.
There is a discrepancy in the reported output current for OP27. Texas instruments says 30mA in their datasheet. On the other hand Digikey reports 20mA.
I also added a voltage regulator 7815 (for +15V) and 79 (for -15V) to supply voltage for opamp. A 0.33uF ceramic capacitor is added on the input side of these regulators. Another 0.1uF ceramic capacitor is added on the output side of these capacitors.
The maximum voltage that can be provided to this circuit should be 0.085V. If the voltage exceeds this, then the OpAmp will be damaged as the current would be more than 20mA.
So, the safe range for input voltage is from 0-0.085 V. The voltage to crystal will be 0-644V. The half wave voltage is achieved at 0.05V of input.