# Tag Info

19

The 555 was designed in the late 1960s - early 1970s, then the usual design method for analog ICs was in a nutshell: think up and draw the block diagram translate the blocks from the block diagram into discrete transistor based circuits (resistors and capacitors can be used as well). For some situations you might want to use special test-ICs that contain ...

15

This circuit was copied out of the RCA Hobby Circuits Manual 1968. Complete entry shown below, including original description of operation.

14

Q2 is a ramp retrace generator. Q1 is a reset comparator when it’s Vbe >200 mV for Germanium. But if Q2-C is low, and Q1-E is high , Q1 is defective due Q1 Vbe defect. Now I see Q2 & Q4 Vbe >1V are both defective Theory of Op. This is a clever little 2 transistor Astable multivibrator with a pulse generator to drive the speaker with a spike from 1/...

12

If you want to know what methodology was used, I suggest you read the book written by the creator of the NE555, Hans Camenzind (RIP). The link above is for a free download. You can also buy the printed book. I have both his books in hardcover. Edit: Jim Williams (RIP), Analog Circuit Design is good too, it's a series of chapters by different folks, including ...

9

To answer the question you didn't ask: In normal operation, with the transistor on, the base-emitter voltage of a bipolar junction transistor is about one diode drop. That's 0.7V for a small-signal silicon transistor (it can be more if the thing's carrying huge currents), and about 0.3V for a small-signal germanium transistor. The direction of the voltage ...

8

In principle, this looks like of especially older acquisition devices worked. Practically, you're still facing a few core problems with your SDRAM: It's non-trivial to work with SDRAM; you must make sure that for the duration of your acquisition, you can count up addresses at 80 MHz, as well as that the SDRAM is able to accept new data every clock. Usually, ...

8

What you are describing is a direct memory access (DMA) operation. It looks like the Teensy 4.1 uses an NXP MIMXRT1062 processor, and that processor does have a DMA engine -- but in order to work for you that DMA engine would have to work with parallel data in, and would have to be otherwise compatible with the ADC you're proposing to use. Unless there's ...

5

I took the time to plug your circuit into the LT-Spice Circuit Simulator and added a reference of 2.5V to the base of Q2. Using a slow ramp pulse input voltage the circuit seems to work as intended. This circuit will work as long as you can live with some specific details: Over the operating range of 0V to 5V on the input expect that it will load the ...

5

I mean...you don't technically need a clock, but if you decided beforehand you want to use a clock then you would need the flip flop. Why would you want to use a clock? It makes timing and synchronization in system easier to control and more predictable which makes it easier to design and test for. Really important in a large, or even moderately sized system....

5

If you redraw your schematic using the normal triangle op-amp symbols it will be easier to understand your circuit. simulate this circuit – Schematic created using CircuitLab Figure 1. Upper circuit redrawn. The idea of a schematic diagram is to show the schema of the circuit. Yours is a very bad example as it it quite difficult to identify the ...

4

It is a link in the copper - not an actual component. Also known as a "net-tie" (thanks @Spehro Pefhany) It looks like it is from Cadence/Allegro. The main value is that it allows nets of different names to be connected. Each of those names may have different attributes (eg trace width). I used one today to force a trace to go to a specific place ...

4

It does work like an SCR as you described. Assume C3 is charged to a higher voltage than the junction of R1 and R2 (about 4V). C3 discharges through R5 and RV1 relatively slowly creating an exponential negative going ramp until the voltage becomes slightly lower than 4V; Q2 will then start conducting. The current from Q2 through R6 will forward bias Q1 that ...

3

Solving for V2: Vout=Vin * R2/(R1+R2)= Vin* 0.3299 So at 10V at V2 you get 3.3V output. simulate this circuit – Schematic created using CircuitLab Solving for I2: Vout = I2*165 Vout = 20mA*165 = 3.3V simulate this circuit In order to use this circuit with 3.3V supply, you should use a rail to rail opamp in order to maximize the output range and then ...

3

"64 kB ought to be enough for anybody" so why not use a FIFO chip? It has all the built-in counters and logic, it will take your ADC data and store it, then deliver it later to the micro at a pace of your choosing. But, of course, it's only 64kB and sells for the price of a 16GB DDR4 stick. And it's pretty oldskool. The Teensy uses a slow QSPI RAM ...

3

Is this intended to be mass-produced and sold to consumers???? EDIT: Instead of adding fuses... since this is a one off build and won't be subject to professional testing.. please drop the AC high voltage off this board completely. You can make a truly safe design using a common wall adaptor. As a bonus, since power supplies are a common failure point, you ...

3

Therefore, Vin, which is negative, would be connected to a virtual ground and, for some reason, this requires to protect the op. amps. with D1. First thing, if Vcc is powered down there cannot be a virtual ground so yes, there could be a situation where a negative voltage appears at the inverting input. Secondly, for every op-amp I've ever used, if $V_{IN}\... 3 This is a Zener diode for over-voltage protection. Ordinarily, a diode conducts only in one direction. However, every diode has a "reverse breakdown" voltage, where the reverse bias voltage across the diode (or, the electric field across the PN junction) becomes great enough for the diode to start to conduct in the opposite direction. Zener Diodes ... 3 First problem is that usually a PP3/LR61 type 9V battery can't provide enough current to power the amplifier to drive an 8 ohm speaker. Otherwise the component values are pretty sane, except for the Zobel capacitor. 1 uF with 10 ohms Zobel network is an RC filter with 3dB point at 16kHz, which is well within audio band. It means that at that frequency you ... 3 Your circuit is OK except for AM7 which is routing all the return current through the Pi's ground which you do not want to do. AM7 is also short-circuiting M1 so all the magnets / lamps will be on all the time (until the Pi burns out). Remove AM7 and you should be OK. simulate this circuit – Schematic created using CircuitLab Figure 1. Tidied-up ... 3 I became aware of this timer when I was 19 years old (1979), and the chip itself had come to market only 8 years prior to that; in 1971. The designer Hans Camenzind was clearly an inventor by nature. He'd originally been hired by Signetics to develop a phase-locked loop (PLL) IC, and later designed an oscillator for these. There was definitely a need for ... 2 You need to be careful here. "... my power pack has a limit of 2A." What happens when you try to draw more current? Will it shut down politely or will it go on fire? Is 2 A the rated maximum (and you have to make sure you don't exceed it) or is it the value at which it will safely limit the current (and you don't have to worry)? You have two loads: ... 2 C in the equation$E = \frac{CV^2}{2}$refers to capacitance. A capacitor with capacitance C which is charged to voltage V has$E = \frac{CV^2}{2}\$energy stored in it. 2 I would suggest a VFD (Variable-Frequency Drive) it should do the job nicely for your application. A VFD can be gotten in the$100 or less depending on source. Another possibility is a inverter drive is a type of motor drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage.

2

I crudely overlaid the two photos you showed to get a better picture of the overall wiring. The transistor appears to be wired correctly. You've got the gate being pulled to ground, driven by a GPIO pin. The drain goes out to your load. The source goes to ground. The most likely cause of failure is that you mixed up the red wires and connected the red wire ...

2

In VHDL, before VHDL-2008, you cannot read from an output signal (after all, it is an output which you can write to, not an input which you can read from). That means that if you cannot read from it in order to manipulate it. You can only manipulate it by completely overwriting it without knowing what it was. So if you do need to read from it to change it (i....

2

You show a 4.7k resistor for the high voltage side LED. At 100V, that would be about 20 milliamperes to the LED. At 30V, that will be about 6 milliamperes to the LED. The LED will light in both cases. A modern LED will still be very bright if operated on "just" 6 milliamperes. There will, of course, be a noticeable difference in brightness between ...

2

Most parts (not just opamps) require that their inputs do not go beyond the power rails by a small amount (usually about 0.3V to 0.6V). With the device powered down, the normal feedback mechanism will not operate because the internal circuits that would normally drive the output to keep the inverting input equal to the non-inverting input are themselves ...

2

There is no contradiction. The behaviour of the simulator is correct. If you drive the inputs of flip-flop EXACTLY at the clock edge, then those values are not guaranteed to be sampled at that clock edge. It will be sampled only at the next clock edge. At least that's what I have observed in many of the logic simulators. You can confirm this if you see that ...

2

I suspect it is a dynamotor to provide high voltages for a mobile, vacuum tube-based radio station of one or another kind, from just a car battery voltage. It is similar by appearance to the dynamotor seen in that Wikipedia article. It probably has military origins and powered up something serious and with transmitter. Just for a car radio, seems overkill. ...

2

Regarding your intent to use germanium and silicon transistors: The circuit can pretty much work with whatever silicon transistors you build it, as long as you don't mistake pnp for npn ones. The reason why PNP ones are germanium and NPN ones are silicon lies in the history of the semiconductor technology. It is easier (i.e. cheaper) to make NPN silicon ...

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