Can You Design a Diode Circuit to Turn On at 5V and Off at 15V?

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A diode circuit is being designed to activate at 5V and deactivate at 15V using resistors and diodes. The initial approach involves using multiple standard diodes in series to achieve the 5V activation threshold, but concerns arise about current behavior at this voltage. The discussion indicates that the current will increase significantly at 5V and then stabilize, which complicates the desired functionality. The participant concludes that achieving the specified behavior may not be feasible without incorporating a transistor into the design. The exploration highlights the challenges of using diodes alone for precise voltage control in this scenario.
sadf
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Homework Statement


Given an input range of voltages (for example, 5-15V), design a circuit using resistors and diodes (and voltage sources) to turn on at input = 5V and turn off at input = 15V. (I chose 5 and 15 arbitrarily).

Homework Equations


The Attempt at a Solution



I am able to get it to turn on at 5V (I would just put about 7 of the standard 0.7V threshold diodes in series), but my understanding is that the current will skyrocket at 5V and then plateau at a voltage slightly higher than 5. I don't know how to get it to continue rising until 15V and then stop there...
 
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Welcome to PF, sadf!

I thought I had an idea, then realized it was wrong.
I now think it is impossible to do this without a transistor.
 
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The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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