# Tag Info

22

I actually own a FY3200S signal generator. When I bought it, I was already aware of the questionable quality of the switching power supply inside it, and the reported high earth leakage currents. For this reason, I replaced the built-in switch-mode power supply by a simple regulated linear power supply (a fairly common mod for these units). If you want to go ...

16

Most people can't hear sinewaves below about 20 Hz. The fact that you couldn't hear them until they got to 100 Hz is probably due to poor low-frequency response in your amplifier/speaker. When you use a square waveform, you are adding a rich series of harmonics to the fundamental frequency — these are what you're hearing, and your brain extrapolates ...

9

If you're considering this: - Combine op amps to generator the square wave Then, the LTC6992 from here appears to do what you want. I am trying to get two off-phase 25% duty cycle square waves(1MHz) to control a full bridge circuit. You might be interested in adding this circuit to the output of the LTC6992 then: - Picture from here and original ...

8

Since you're new to electronics I simplify here a little bit: OpAmps don't have the current drive capability to drive speakers directly. Speakers usually have a impedance in the low ohms. 8 Ohm is typical. A ordinary OpAmp won't drive much more than 50mA to 100mA. At 10V Signal that is roughly equal to an impedance of 1000 to 2000 Ohm. Much higher than ...

8

As low-tech as it sounds, I recommend using two lithium 9V blocks. It's simple, cheap, portable, has no mains nor buck converter artifacts. And it can sit on your shelf for years and just works when you need it – anywhere.

7

No, that won't work. You could use fixed voltage supplies (AC adapters, wall warts) for most power supply purposes - just understand that your circuits are living dangerously if the supplies aren't current limited, so be careful and double-check your connections - until you can afford an adjustable PSU. One option is to make one of your first projects an ...

7

You should just plug this circuit topology into circuit simulator and start experimenting to figure out on your own how these work. This way you will learn the most. These circuits use one transistor as a constant current circuit (sinking in your left circuit / sourcing in the right circuit) to linearly discharge / charge the capacitor. The other transistor ...

6

The function generator has a BNC output. There are a lot of pieces of test equipment that use this connector, including oscopes. You can find many different types of BNC cables. You can get ones with probes, clips, bare wires, or BNC to BNC. You can even get BNC spliters if you want to split your signal to multiple places. What one you get (and the quality, ...

6

Although I still wasn't able to find a manual online, in an ad for one of the products for the similar SG100x series (same as mine w/o an ADC or second TTL port), it mentions the sweep function going from frequency f1 to f2. As mentioned in my question, I couldn't find any direct way to set the starting and ending frequencies, but seeing them labelled f1 ...

6

Your meter reads AC in $V_{rms}$, which is very different from $V_{pp}$. For sinusoidal signals: $V_{rms} = 0.3535 \cdot V_{pp} = \frac{1}{2\sqrt{2}} \cdot V_{pp}$ And therefore $5V_{pp} = 1.767 V_{rms}$ Also, because you've set your DC offset to 0V, the DC average of the sine wave is 0V, hence the $0V_{dc}$. Therefore, both your ...

6

There are several things wrong here. You say you want to drive a 8 Ω speaker with 15 W. That means you need sqrt((15 W)(8 Ω)) = 11 V. Note that this is RMS. For a sine wave, that means that the peak voltage is sqrt(2) higher, or ±15.5 V. Clearly ±10 V supplies aren't good enough. Then there is the issue of providing enough ...

6

Two reasons. First, a TTL input is actually an output. It sources a current that must be shunted to ground to be seen as a logic 0. This current affects the charging rate of the timing capacitor, adding to the current from the output through the timing resistor. Above 2.4 V the input no longer sources current out the input pin. When the output goes low, ...

6

CMOS Schmitt triggers have the two threshold voltages at $\frac 1 3 V_{DD}$ and $\frac 2 3 V_{DD}$. Furthemore $V_{OH}=V_{DD}$ and $V_{OL}=0$. Since this is symmetric with respect to $V_{DD}/2$, it follows that the timings $T_H$ and $T_L$ are approximately equal, from the equations:  V(t=T_H)=V_{t+}=\frac {2}{3}V_{DD}=V_{DD}+(\frac {V_{DD}} ...

6

1) I don't see why not. The article has the manufacturer's name on it, much more reputable than 'some guy off the internet'. Without actually building or simulating it, or doing calculations around R2/3 C2 values (the only bit that isn't 'obviously OK'), this guy off the internet (me) thinks it all looks perfectly plausible, the concept and block diagram are ...

5

Looks to me to be a "163" obsolete-standard line cord. You may want to consider removing the existing socket and hard-wiring a locale-appropriate line cord to the instrument (at your own risk) - make sure that the 'line' goes to the fused path! Another (perhaps safer) option would be to leave the socket in place (cutting off the wires coming from it), ...

5

The 50 Ohm internal resistance changes the behavior from that of an ideal signal source is one simple manner: It behaves just like adding a 50 Ohm resistance in series with the voltage source, completing the circuit through your load: simulate this circuit – Schematic created using CircuitLab As the function generator is specified with an internal ...

5

Here are a couple of possible reasons the reading could be wrong: The signal generator's output impedance is high. Some signal generators do not have a voltage-follower output buffer stage, hence while the nominal voltage of the output signal at infinite load resistance would match the actual voltage, the voltage drops significantly the moment come current ...

5

You break it down into its different phases of operation. Yes, C1 is a filter capacitor; it's just there to make sure that the "reference" voltage going to the inverting input of U1A and the noninverting input of U1B is as noise-free as possible. Yes, U1B is an integrator. It is simply integrating the output of U1A — which in turn must be a square ...

5

If the function generator can produce the 50 Hz signal, then there is no advantage to the 555 timer electrically. Function generator advantages: Ready to use, just dial in what signal you want. 555 timer advantages: It makes you learn about a 555 timer. If you don't value your time (or your professor doesn't), it's a lot cheaper than a function ...

5

It's a bit hard to answer without a schematic, but a rotary switch is a typical solution. You can get them in many different configurations. For example, a four position double pole switch as shown below.

5

The basic difference is that a sine wave is only a single frequency, but a square wave is actually made up of the fundamental frequency plus odd harmonics. So for example a 50Hz square wave isn't just 50Hz, but also 150Hz (3 x 50HZ), 250Hz (5 x 50Hz), 350Hz (7 x 50Hz) etc. Amplitude decreases as the harmonic number increases, but may still be significant ...

4

It should work more-or-less. The LM348 is kind of a quad $\mu A741$, so it has a class AB output stage. The LM358/LM324 has a different kind of output stage that is more prone to crossover distortion. You might want to use a pullup resistor of 5 or 10K from the sine and triangle outputs to +9V to help reduce crossover distortion (by forcing it into Class ...

4

In addition to the normal attenuation at increasing frequencies (as @ChrisStratton and OP pointed out), there is the potential to unwittingly add a low-pass filter to the output by decoupling it. This is based on the fact that the trace (or wire) between the DDS output and the decoupling capacitor will have some resistance, which combines with the capacitor ...

4

That's a pretty much standard way of generating a triangular wave. R1, R2, C1 provide a stable voltage reference. As you sense C1 is there to stabilize it in some ways, it's there to suppress noise, and that's not a strange place at all. The reference voltage is 1.85V U1A, together with R3 and R4 is wired as a comparator, its input being the green node, ...

4

You could easily do a highly flexible DDS on an STM32F4 Discovery board for ~$15 using an internal DAC, DMA, a timer and a sine lookup table. People have blogged examples of similar things if you look for them. In order to get the required frequency (the STM32F4xx DAC's can only do 300ksps at full swing, which equates to ~1V/$\mu$s) you will need to ... 4 The function generator you are referring to is an arbitrary waveform generator. You can actually punch in a DC signal and live with that. The specs on the rigol site states that the maximum peak to peak output voltage for channel 1, that is the stiffest, is 10V on a load of 50$\Omega$. Assuming the output is ground referenced you have some 5V on 50\$\...

4

The right hand op-amp looks like a comparator (with an open collector output). The emitter I suspect is pin 1 and this is tied to -15 V. Open collector outputs require a pull-up resistor hence the need for R5 in your circuit. If you could link where you found this circuit this could be confirmed. I think the comparator matches the pin out of the LM311: - ...

4

Op-amps don't have the grunt for this An ordinary op-amp is designed to drive small-signal loads such as small headphones, the inputs of other amplifiers, or other circuits. A 8Ω speaker simply requires too much current (amps vs millamps) for an op-amp to drive it alone. But, boosting the output current is simpler than it sounds Fortunately, it's ...

4

Your example circuit shows a Schmitt-trigger inverter. Look at the threshold voltages in the example table...their average is less than half-Vcc: The capacitor charges toward Vcc (or Vdd) faster than it discharges toward ground. This voltage threshold asymmetry is a major contributor to pulse-width asymmetry. If Schmitt thresholds were symmetrical about ...

4

All signal generators need a reference for the signal. Your old sig-gen likely had the output referenced to mains ground while your PC one may be floating. Assuming, that is, that whatever you are feeding is also referenced to the same ground. Reliance on the mains ground can be problematic though. Using the reference supplied from the signal generator is ...

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