Hi All,
Please consider my circuit and check whether I have calculated my current correctly.
Please check the order of my steps and approach is correct. I am trying to do it accurately.
Part Number of Q114  https://www.onsemi.com/pub/Collateral/MMBTA55LT1D.PDF
Part Number of Q103  https://assets.nexperia.com/documents/datasheet/PDTC123J_SER.pdf
The load current of the circuit .i.e. Collector current of Q114 is 30mA (which I have calculated previously)
Apart from this load current of 30mA, I need to calculated the current in this 3.3V Rail for which I have calculated below.
1. Minimum Resistance of R139 = 950Ohms
2. Maximum Resistance of R139 = 1050Ohms
3. Maximum Input Voltage = 3.3 * 1.02 = 3.366V (Considering 2% tolerance)
4. Minimum Input Voltage = 3.3 * 0.98 = 3.234V (Considering 2% tolerance)
5. Maximum Load current through the collector Q114 Ic = 30mA
6. Maximum Collector Emitter Voltage Q114 Vce(sat) = 0.05V (Taken from Fig.6 graph in the datasheet for 150degC)
7. Minimum Base current Q114 Ib = Min Input Voltage/Max Resistance = 3.234/1050 = 3.08mA
8. Base Emitter Voltage of Q114 Vbe = 0.88V (Taken from Fig.7 graph in the datasheet for 55degC)
9. Collector Emitter Voltage of Q103 Vce = 0.045 (Taken from Fig.7 graph in the datasheet for +100degC) (Since the collector current of Q103 is the base current of Q114 = 3.08mA)
10. Maximum Current = (Max Input Voltage  Vbe of Q114  Vce of Q103)/Min Resistance of R139 = (3.3660.880.045)/950 = 0.002569474 ~= 2.5mA.
Please check my work. I have attached my circuit. Your feedback will be really helpful to me.
Thanks.
Please consider my circuit and check whether I have calculated my current correctly.
Please check the order of my steps and approach is correct. I am trying to do it accurately.
Part Number of Q114  https://www.onsemi.com/pub/Collateral/MMBTA55LT1D.PDF
Part Number of Q103  https://assets.nexperia.com/documents/datasheet/PDTC123J_SER.pdf
The load current of the circuit .i.e. Collector current of Q114 is 30mA (which I have calculated previously)
Apart from this load current of 30mA, I need to calculated the current in this 3.3V Rail for which I have calculated below.
1. Minimum Resistance of R139 = 950Ohms
2. Maximum Resistance of R139 = 1050Ohms
3. Maximum Input Voltage = 3.3 * 1.02 = 3.366V (Considering 2% tolerance)
4. Minimum Input Voltage = 3.3 * 0.98 = 3.234V (Considering 2% tolerance)
5. Maximum Load current through the collector Q114 Ic = 30mA
6. Maximum Collector Emitter Voltage Q114 Vce(sat) = 0.05V (Taken from Fig.6 graph in the datasheet for 150degC)
7. Minimum Base current Q114 Ib = Min Input Voltage/Max Resistance = 3.234/1050 = 3.08mA
8. Base Emitter Voltage of Q114 Vbe = 0.88V (Taken from Fig.7 graph in the datasheet for 55degC)
9. Collector Emitter Voltage of Q103 Vce = 0.045 (Taken from Fig.7 graph in the datasheet for +100degC) (Since the collector current of Q103 is the base current of Q114 = 3.08mA)
10. Maximum Current = (Max Input Voltage  Vbe of Q114  Vce of Q103)/Min Resistance of R139 = (3.3660.880.045)/950 = 0.002569474 ~= 2.5mA.
Please check my work. I have attached my circuit. Your feedback will be really helpful to me.
Thanks.
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