CA3046 VCA

Using discrete transistors from a transistor array, this circuit avoids an OTA altogether. It uses one transistor as a Gilbert multiplier to predistort the signal, so that a larger signal can be fed into the circuit. The circuit is based on the one described in Modulus issue 5, that was provided by Chris Crosskey.
I have modfied it with a trimmer to adjust the DC offset and adjusted the input sensitivity and output gain to give some headroom and unity gain. This VCA has a linear response. A diode has been added on the control input, to block out negative voltages, which cause DC on the output. Because of the diode, the control caracreristics is unlinear below 1 volt.
The predistortion really works in this circuit. The distortion stays low up to a point where it suddenly increases dramatically. With the chosen resistor values, that point is well above normal signal levels.
Noise figures for this circuit is comparable to the SSM2024 and the LM13600 but signal bleedthrough is not as good. On the other hand, CV bleedthrough is lower than the LM13600, with proper trimming.


CA3046

700W Power Amplifier with 2SC5200 & 2SA1943

700W Amplifier Adjust the amplifier power 700W looks calm, but we requirement not put out of your mind to the adjustment happening forcing transistors, the whole relating to-engagement of frequency offset. It is compulsory to change the current insurance rule which serves to guard the final transistors. Their tendency to happen allowable to keep the transistors in the SOAR characteristics. primary it was needed to evaluate all the necessary resistors and subsequently measured to verify the accuracy of the calculations, it is managed with satisfactory results. Peripheral changes required in support of it to be there able to consistently amplifier to supply power. - First you need to restore the 2k2 resistors stylish string with the LEDs on Zenerovými resistors with upper wattage. be enough 1/2W resistors, power loss next to 80V +-based 1W. - therefore was traded 1k2 resistor in the pointer resistor by the side of 620 ohms.


Which is the initial reap has doubled, so at this point is the overall gain amplifier 40 and the limit excitation is sufficient to 1V rms. - Předbudiči transistors were replaced by stronger MJE15032/33 since KF467/470 are permitted satellite dish current 20mA - by the side of the exciter output stages are used the same transistors for example the output stage. - add up to of terminals of transistors has been increased to eight pairs - It had to occur to compensate designed for the excitation level by calculation a capacitor 10pF to 47pF + 22K appendage. This led to a slight "gradual" amplifiers, but this did not affect the ensuing parameters. This power is tuned correctly in support of this type of terminal transistors 2SA1943/2SC5200.

With with the purpose of it is a least assessment next to which the amplifier operates stably exclusive of pass by the side of the rising and falling edges of the genuine. - The ultimate adjustment, the adjustment terminal current protection transistor. The SOAR transistor characteristics shows with the intention of the most allowable radio dish current once the voltage of 1.5 A is ideal in favor of cooling, so it's essentially not as much of. Therefore, the current protection is customary to 12A, single-arm. This impersonate protection SOAR transistor characteristics. curt-circuit current is regarding 6 A which is about 075A for every transistor. This is far beneath the SOAR characteristics. The mechanical design is relatively clear-cut, the transistors are placed on the two cooling profiles with a height of 66 mm, width 44mm, overall part 260mm. They are twisted contrary to each one other in this way, from the cooling tunnel. Coolers are attaching the nylon aid which allows the compilation of transistors exclusive of washers, and thus better conveying tepla.DPS amplifier next to the top of the tunnel and the transistors are soldered from the underside of PCB.

SPS250A power supply 2SC2625

A SMPS I take on trips I forgot is NOT auto voltage sensing on input and was still set to 110V after recent US trip.

Pretty obviously the power transistors got fried and rather than junk it I thought I should fix it

This is dealing with mains voltage so do not do this unless you know what you are doing as the voltages are lethal.

It took a bit of digging to find the circuit diagram (thought it was on the pdf that came with it), still haven't found it exactly but this is very similar except mine appears to run the fan full all the time instead of having a fan control board on the lower right here.


These power supplies are widely in use and all are called SPS250A in the name and are all made in China under various names... so if yours has SPS250A in the name and looks like mine then chances are it is the same but no responsibility if it is not, use information at own peril (and this is running at mains voltage which can kill so do not do this without a healthy respect for high voltages).

The two NPN power transistors 2SC2625 were removed still attached to their heatsink.


Note all the common mode filtering on the input side (top right corner).
Mine has had the right hand transistor crater and the other is short circuit between the pins.

Anyway suffice to say power supply can be easily repaired.

I hear that it might make sense to replace the 2Sc2625 10A versions with 2Sc3220 which are 15A versions but I would source them in HQEW.net  .

2N3906 PNP General Purpose Transistor

The 2N3906 is the general purpose (PNP Silicon) PNP switching transistor, which is produced by Fairchild Semiconductor.

2n3906 absolute maximum ratings: (1)Collector–Emitter Voltage: 40 Vdc; (2)Collector–Base Voltage: 40 Vdc; (3)Emitter–Base Voltage: 5.0 Vdc; (4)Collector Current — Continuous: 200 mAdc; (5)Total Device Dissipation, TA = 25℃: 625mW; (6)Total Power Dissipation, TA = 60℃: 250 mW; (7)Total Device Dissipation, TC = 25℃: 1.5 Watts; (8)Operating and Storage Junction Temperature Range: –55 to +150℃.

2N3906 features: (1)Capable of 600mW of Power Disspation and 200mA Ic; (2)Lead free finish/ROHS compliant; (3)Epoxy meets UL 94 V-O flammability rating; (4)Moisure sensitivity level 1; (5)Through Hole pakage; (6)Marking: type number.

The CA3046 was pure simplicity

When you learn about making things like amplifiers in EE class, you learn about how important it is to have matched pairs of transistors. Symmetry tends to be just as important in electronic circuits as it is in plant life: pairs of tubes supply and remove fluids from a plant leaf much the same way electrons flow through paired transistors in an amplifier. Optimal behaviour occurs when these sides respond in a balanced, symmetrical manner (in the most common cases.)

The more closely you can match the behaviour of these 2 transistors, the more symmetrical the circuit becomes. So, someone got the bright idea — what if we put more than one transistor on the same piece of silicon? Thus, the integrated circuit was born: not with the goal of putting computers on chips (or anything digital, for that matter), but with the idea of making the performance of a circuit uniform.

The earliest ICs only had simple transistors on them. The CA3046 was pure simplicity: 5 matched NPN type BJT transistors on the same chip. You could continue to build circuits the way you were used to — with resistors and capacitors on the circuit board or prototype board — and simply replace the transistors in there with matched transistors, formed from the same piece of silicon. Presto, your circuit sounded a lot better. If you went high volume, you could have your circuit burned into its own integrated circuit; many opamps (the building block of modern analog circuit design) were designed this way. Or you could create a printed circuit board, and go that way — the sort you might have seen in just about every consumer electronics product in the 1970s and 1980s.

The CA3046 (and its strange partner, the CA3096: 3 NPN, 2PNP in a single chip) helped us ring in an age of harmony. Matched pair transistors were essential to building harmonic circuits that were pleasing to the ear. The original Moog “transistor ladder” design required hand matching of transistors; were the CA3046 available then, Moogs probably would have been a lot cheaper (had they not already become a “fad”)  .

Later I had a few missed starts trying to make circuits: a failed design for a video game emulator cartridge that was already halfway into production nearly bankrupted me, and I lost heart. I put away my skills for many, many years, always thinking that i could fall back on it if I really needed to. Now I see it’s a skill I’ve neglected for far too long, and one that can enrich my life if I only take the time to apply it artfully. 

Popular Transistors MMBT3904

This is the MMBT3904 NPN SMT Transistor Design Kit. It includes the very popular SMT version of the 2N3904, General Purpose NPN Transistor: MMBT3904. This was one of the most popular transistors used in all kinds of circuits for years and years. It was designed for general purpose amplifiers with a 500 milliamp Collector current requirement. This kit also includes a few pieces of the MMBT3906 (PNP) which is the complement to the MMBT3904 (NPN) and a SMT Voltage Regulator, LM317M in the SMT package. 


This kit also includes a tremendous amount of different SMT components that you would use to develop numerous circuits. Included are different values of SMT Transistors, SMT Resistors, SMT Aluminum, Ceramic & Tantalum Capacitors, SMT Inductors, SMT Signal (Single & Dual) & Zener Diodes, SMT Trimpots, SMT LEDs, Pushbutton Switches, an Electret Microphone, and a miniature Speaker. It also includes some electronic hardware that are used in most projects for I/O.