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I'm trying to simulate a simple signal amplifying circuit using three transistors as shown below:

Falstad Circuit, closed switch

(Note that the LED isn't turned on)

But when I open the switch, the current still flows normally from the 9V source on the left, even though the first transistor's base doesn't receive tension. The current has the same value as before if you look at the bottom right corner. It should be zero.

Here's the image:

Falstad circuit, open switch

I'm very new to electronics and studying it on my own.

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  • \$\begingroup\$ Just to clarify, the 9V source i mention is the one to the right of the LED and the 220Ohm resistor, just before the second switch. \$\endgroup\$
    – Nihilo
    Dec 15, 2023 at 15:43
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    \$\begingroup\$ 10 V applied through the switch without a serial resistor is not really a good thing. And you need also to wire the negative "pole" of this voltage. However, transistors are characterized by a current Icbo (very very low) ... current through transistor with an "open base" ... which explains that you can measure a current ... at least through the diode. \$\endgroup\$
    – Antonio51
    Dec 15, 2023 at 16:14
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    \$\begingroup\$ Also note that because you don't have any ground reference, opening or closing the switch has absolutely zero impact on the circuit. There's nowhere for any current to flow from the +10 V input. \$\endgroup\$
    – Hearth
    Dec 15, 2023 at 16:30
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    \$\begingroup\$ Presumably you want the negative side of that battery supply to be ground, right? That's where you should put your ground symbol. This is still not a correct circuit, though, because there's no current-limiting on the base of your transistors. \$\endgroup\$
    – Hearth
    Dec 15, 2023 at 16:47
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    \$\begingroup\$ (With a proper input signal and a base resistor, 220 Ω still was a bit low (assuming 10 V for the battery) and 100 kΩ way high.) \$\endgroup\$
    – greybeard
    Dec 15, 2023 at 20:13

1 Answer 1

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As already pointed out by others in comments ...
With the resistor at the input and wired ground of the 10 V, you should have a circuit like this.

Made with microcap v12

enter image description here

NB: when the switch is open, values of currents and voltages are not very "meaningful".
The circuit is not really "complete".

Here is an example of some "resistors" added (switch open).

enter image description here

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