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In my view, both BJT's and FET's are voltage controlled current sources more than anything else, but they have major differences in their voltage-to-current transfer characteristics. The drain current of an FET depends quite linearly on its gate-source voltage. Likewise, the collector current of...
Bipolar junction transistors are voltage controlled. The fact that the base current and collector current have a fairly constant relationship does not mean that variations in the latter are caused by variations in the former, or vice versa. It would be grossly unscientific to assume so.
This...
(EDIT: Link to original code: ASM (NASM) | [ORG 0x100] [BITS 16] ;--- - Bubblesort NASM - sVj8QSce - Pastebin.com)
For some reason NASM would crash on my '486 -- this is written for TASM:
.286P
CODE SEGMENT
ASSUME CS:CODE,DS:CODE
ORG 00100H
PUSH CS
POP DS
MOV BX, OFFSET S
CALL BSORT
MOV AX...
The oscillator should be able to work with the current resistor values. However, the L/C ratio seems too low -- I would use 1...2 uH (or more) for the inductor. Also, the 100 nF capacitors may have a relatively large parasitic inductance at 27 MHz, resulting in loss of signal; therefore, 10 nF...
This could be an explanation:
Tuned at 780 kHz, the preselector might fail to reduce the strong 850 kHz signal sufficiently. The mixer (or any RF amplifiers ahead of it) then would get overloaded, generating the 2nd harmonic of the latter signal -- which would be at 1700 kHz.
If the local...
You're right; C7 is part of the tank circuit and should be paralleled with a capacitor more suitable for RF. It's done in this circuit which otherwise is almost the same (note that C7 is labeled here as C5):
Above, the connection between the collector of VT1 and the rest of the circuitry is also...
Re: BJT max Vbe and Ib
For reliability, I would limit the base current to less than 10...20mA. I think 43mA is a bit on the high side.
If that's a forward voltage then it's too high. The reverse voltage can be 6 volts according to the datasheet (https://www.fairchildsemi.com/ds/2N/2N3904.pdf)...
Hi,
The circuit can be used as an FM transmitter but it's likely to have poor frequency stability and harmonics in its output. Also, the tuned circuit in the oscillator isn't isolated from the antenna, so when something moves near the antenna, the frequency may change.
It's a good idea to...
Hi,
There are different ways to generate AM modulation but I'm not too familiar with them, so I'm just re-posting the schematic as a .PNG file for easier viewing. That said, it looks like the collector and emitter resistors are too large; I wonder if the oscillator really works (it may work in...
Hi,
If you generate the sound by printing a BEL character (using DOS or BIOS), the sound duration and pitch will usually depend on the code in the BIOS INT 10h handler (which also gets invoked by DOS INT 21h, I think) unless you write your own INT 10h routine.
It's possible to directly write...
When measuring the AC voltage at the collector against ground in this circuit, there is a DC offset equal to +Vcc to be considered. I have also noticed that the readings are different, even after this offset (+5V) has been subtracted (resulting in +7V and -3V for +12V and +2V, respectively). One...
There is clearly too much damping in the first circuit shown; it cannot sustain oscillation. With a 100pF capacitor from the collector of the 2N3904 to its emitter and another 100pF capacitor across the 1.1K resistor, it would likely oscillate. The emitter decoupling capacitor could also be...
That makes things a great deal simpler than with many other types of batteries. I recommend using a constant-voltage charge at the float charge voltage and with current limiting, as IanP suggested.
The float charge voltage is somewhat critical:
(https://en.wikipedia.org/wiki/Float_voltage)...
An important thing to consider when charging batteries is the battery chemistry (NiCd, NiMH, Li-ion, lead acid, etc.).
Discharged lead-acid batteries cannot be charged full within a few hours. Lead-acid batteries require 10 hours or more to charge full if they are discharged.
Additionally...
;16-BIT ADDITION
;AX:BX:CX := AX:BX:CX+DX:SI:DI
ADD CX, DI
ADC BX, SI
ADC AX, DX
JC OverFlow
;THIS IS OTHERWISE THE SAME AS IanP'S EXAMPLE
;EXCEPT THAT 16 BIT REGISTERS ARE USED
;----------
;MULTIPLY DX:AX BY DI:SI, RESULT IN DI:SI:DX:AX (64 BIT)
PUSH BP
MOV BP, SP
SUB SP, 8 ;MAKE ROOM
;ON...
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