You have in your possession as many (identical) diodes as you want (with exponential IV characteristics and one point \( (V_{D} = 0.7V, I_{D}=20mA) \)
with \( n=1 \) and \( V_{T} = 25mV \). Remember that \( I_{D} = I_{ss} \cdot e^{\frac{V_{D}}{n \cdot V_{T}}} \)
Using one current source \( I_{in}=4mA \) and by combining diodes in series and parallel, design a circuit that produces an output of \( V_{o} = 1.25V \)
Solution (as far as I went):
Using the IV point I can calculate Iss: \[ I_{D} = I_{ss} \cdot e^{\frac{V_{D}}{n \cdot V_{T}}} <=> I_{ss} = I_{D} \cdot e^{\frac{V_{D}}{n \cdot V_{T}}} = 20mA \cdot e^{\frac{0.7V}{1 \cdot 25mV}} <=> I_{ss} = 1.38 \cdot 10^{14}A \]
I also attached a pdf file with the circuit that I tried to design but I couldn't in the end. I just can't think of how to combine diodes in parallel and series in order to produce the desired output.
Question 1)
Can you show me a solution and try to make understand how to approach similar problems? Do not show me the math, only the circuit and let me
do the math to see if it actually works.
Question 2)
How should I think when designing diode circuits?
For example, I know that if I put 2 diodes in parallel and one is reversed, they can't conduct current at the same time. Are any other
stuff like that, that I need to know and take into consideration while designing diode circuits?
Thank you!
PS: In the pdf, the Greek text is the exercise pronunciation which I translated for you at the beginning of this post.
with \( n=1 \) and \( V_{T} = 25mV \). Remember that \( I_{D} = I_{ss} \cdot e^{\frac{V_{D}}{n \cdot V_{T}}} \)
Using one current source \( I_{in}=4mA \) and by combining diodes in series and parallel, design a circuit that produces an output of \( V_{o} = 1.25V \)
Solution (as far as I went):
Using the IV point I can calculate Iss: \[ I_{D} = I_{ss} \cdot e^{\frac{V_{D}}{n \cdot V_{T}}} <=> I_{ss} = I_{D} \cdot e^{\frac{V_{D}}{n \cdot V_{T}}} = 20mA \cdot e^{\frac{0.7V}{1 \cdot 25mV}} <=> I_{ss} = 1.38 \cdot 10^{14}A \]
I also attached a pdf file with the circuit that I tried to design but I couldn't in the end. I just can't think of how to combine diodes in parallel and series in order to produce the desired output.
Question 1)
Can you show me a solution and try to make understand how to approach similar problems? Do not show me the math, only the circuit and let me
do the math to see if it actually works.
Question 2)
How should I think when designing diode circuits?
For example, I know that if I put 2 diodes in parallel and one is reversed, they can't conduct current at the same time. Are any other
stuff like that, that I need to know and take into consideration while designing diode circuits?
Thank you!
PS: In the pdf, the Greek text is the exercise pronunciation which I translated for you at the beginning of this post.
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