Cascode substitutions

Started by Tim Williams in sci.electronics.design7 years ago 76 replies

Designing an RF amplifier. Concept is, high power, complementary cascodes for the output stage (with heavy class A use, but being PP, class AB...

Designing an RF amplifier. Concept is, high power, complementary cascodes for the output stage (with heavy class A use, but being PP, class AB is an option). 50 ohm output, direct drive, say 10W level. I happen to have a complementary pair that's not too slow (2SC2690A and 2SA1220A), and I'd like to maximize the bandwidth around that. The NPN side is fine, I have a 30V, 1A, 2GHz tran...


OT: Electronic Design!

Started by Cursitor Doom in sci.electronics.design3 years ago 20 replies

In a surprise change from the usual topics discussed in this group, I'm posting a question about electronic design! Win kindly reposted this...

In a surprise change from the usual topics discussed in this group, I'm posting a question about electronic design! Win kindly reposted this enhanced schematic of an amplifier board I've been troubleshooting:- https://www.dropbox.com/s/o4tybr81cefbk5n/8565A_amp.GIF?dl=1 My question relates to the voltage-to-current section which comprises 6 transistors plus various passive 'support'...


Ft doubler

Started by Jeroen Belleman in sci.electronics.design3 years ago 5 replies

We had a rainy weekend here and I decided to spend some time simulating Battjes' Ft doubler and to compare it with a more ordinary differential...

We had a rainy weekend here and I decided to spend some time simulating Battjes' Ft doubler and to compare it with a more ordinary differential cascode amplifier with similar gain and bias conditions. I sort-of expected to find that the bandwidth of the Ft doubler would roughly be twice that of the simple differential stage, but I did not find that. In fact, the bandwidth is about the sam...


Writing to MCU flash

Started by Phil Hobbs in sci.electronics.design4 years ago 108 replies

So we've got this custom product that includes a voltage-controlled amplifier. VCA chips as used in ultrasound and so on have nice low noise...

So we've got this custom product that includes a voltage-controlled amplifier. VCA chips as used in ultrasound and so on have nice low noise at the highest gains, but at low gain they stink on ice. The same is true of all transconductance-based VCAs unless you use a zillion stages. Sooo, we're faking it with a dpot, an op amp with a mux-controlled resistor ladder, and an LPC804 Cort...


Design Error 2 extra

Started by Phil Allison in sci.electronics.design3 years ago 6 replies

Hi to my tormenters, --------------------- the tube amp question left most of you a tad agog. Yet it was simply a case of noting that...

Hi to my tormenters, --------------------- the tube amp question left most of you a tad agog. Yet it was simply a case of noting that opening the s/b switch altered the topology of the amplifier in a not good way. Since transient over-voltage on the plates leading to insulation failure is a common thing with tube amps generally, many makers apply a simple fix using high voltage dio...


Noise and gain in transimpedance amplifiers

Started by Anonymous in sci.electronics.design7 years ago 34 replies

Hi, I have a few questions about gain and noise in the transimpedance amplifier. I've been mainly reading Hobbs (2nd edition) and H&H AoE (3rd...

Hi, I have a few questions about gain and noise in the transimpedance amplifier. I've been mainly reading Hobbs (2nd edition) and H&H AoE (3rd Ed). References below are to those editions. Most importantly, thank you to the authors for these wonderful texts! === Rolloff of transimpedance === Hobbs Eqn 18.10 gives an expression for the transimpedance Zm, and states t


Mains power puzzle

Started by Phil Allison in sci.electronics.design3 years ago 118 replies

Hi to all my pals, on the bench I have a US made, bass instrument amplifier (Eden) in near new condition. It uses a 600VA toroidal tranny...

Hi to all my pals, on the bench I have a US made, bass instrument amplifier (Eden) in near new condition. It uses a 600VA toroidal tranny in the PSU. The "T5A" 20mm AC fuse installed was blown and also a similar previous fuse, I'm told. Nothing wrong found with the amp when a new fuse was fitted. However, repeated switch on testing shows max, peak inrush surges over 120 amps, either ...


X5R vs X7R MLCC

Started by Anonymous in sci.electronics.design4 years ago 207 replies

I use a 1210 X5R 25V 10% MLCC for input DC blocking. Supply is drying up and I want to place an order to support production for a while. In...

I use a 1210 X5R 25V 10% MLCC for input DC blocking. Supply is drying up and I want to place an order to support production for a while. In performing a Digikey/Mouser search I see there are now X7R devices in the same footprint. I know the X7R will be more stable under DC voltage which is an advantage *if* there is much DC on the input. The amplifier circuit has a 6 volt DC bia


What's Wrong with the DC300A ?

Started by Phil Allison in sci.electronics.design3 years ago 26 replies

Hi to all my fans, -------------------- see pic of possibly the most famous stereo power amplifier ever...

Hi to all my fans, -------------------- see pic of possibly the most famous stereo power amplifier ever made. https://cdn11.bigcommerce.com/s-6naz0isypk/images/stencil/2048x2048/products/3247/20471/5569873- 7432-5__81144.1510738289.jpg?c=2 The Crown DC300A was first released in the early 1970s and sold in large numbers, world wide. The letters "DC" refer to the fact it has response dow


Transimpedance amplifier (TIA) oscillating at above 1 GHz. Need Help

Started by Anonymous in sci.electronics.design9 years ago 41 replies

Hey Folks, I need to design a broadband TIA for photo current amplification. I am using a LMH6629. I simulated the circuit in Tina-TI an it...

Hey Folks, I need to design a broadband TIA for photo current amplification. I am using a LMH6629. I simulated the circuit in Tina-TI an it is working pretty well for a feedback resistor of 330Ohm and a feedback cap of 4pf and a signal of 10MHz. However the simulation is showing oscillation if I increase the cap to something above 20pf. In my opinion it should be stable for higher caps and o...


Looking for a replacement for NXP/Philips TDA7052A/AT NXP 1W audio amp going obsolete...

Started by boB in sci.electronics.design6 years ago 15 replies

This part, an 8 pin bridgable 1W audio amplifier with volume control input is going obsolete and last order date is end of this...

This part, an 8 pin bridgable 1W audio amplifier with volume control input is going obsolete and last order date is end of this year. When I designed it in around 10 years ago they were old then but plenty available. We will eventually need to design in a replacement. We are running these at around 9V VCC and they work great into a small speaker. 8 Ohms I believe. We also use...


Phototransistor fed to a transimpedance amplifier

Started by SilverLeo in sci.electronics.design6 years ago 45 replies

Hi all. I'm running through some test of a phototransistor signal conditioner, and I'm facing with wild noise issues. The conditioning is a...

Hi all. I'm running through some test of a phototransistor signal conditioner, and I'm facing with wild noise issues. The conditioning is a basic TIA stage: http://i.imgur.com/PcgglKZ.png Feedback resistor is 5K, feedback capacitor is 470pF, negative bias is -12V, and photocurrent is in the range 8uA-800uA. The bandwidth should be about 50kHz. Opamp is OPA2277UA. Problem is that phototrans...


using an smt resistor as a fuse

Started by Winfield Hill in sci.electronics.design4 years ago 32 replies

I've placed 22-ohm 0805 resistors in series with the HV supply lines in the latest version of my easy-to-build AMP-62 high-voltage amplifier...

I've placed 22-ohm 0805 resistors in series with the HV supply lines in the latest version of my easy-to-build AMP-62 high-voltage amplifier board. This version is often made with aggressive output current-limit values, e.g., 150mA. But it's intended that such currents last only a short time, e.g., to rapidly charge a capacitive load (during the rapid output slewing, the 22-ohms only drops ...


Audio Generator or Function Generator? Which to get?

Started by Anonymous in sci.electronics.design6 years ago 78 replies

I've been looking into buying an Audio Generator (Sine and Square Wave). I mainly want this to run thru an amplifier to listen to the...

I've been looking into buying an Audio Generator (Sine and Square Wave). I mainly want this to run thru an amplifier to listen to the frequency repsonse of the amp and speakers. Nothing very scientific, just to see what these amps and speakers can do.... And on occasion to inject an audio signal into amp sections to dee if the audio is passing that stage. Originally I was looking at some ...


Microstrip wideband AC coupling

Started by John Larkin in sci.electronics.design12 months ago 9 replies

https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1 0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that the...

https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1 0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that the 0204 is best. In the 25 ps sort of domain, on FR4, there's no need to buy exotic caps. That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my distributed amplifier, it loses 80% of its capacitance. -- If a man will begin with certa...


discrete JFETs vs CMOS analog switch

Started by Adam Seychell in sci.electronics.design2 years ago 29 replies

I need a switchable 0 /40dB attenuator for a 10Hz-20MHz 1Vp-p signal into a buffer amplifier (10k|3pF input loading). First I thought of using a...

I need a switchable 0 /40dB attenuator for a 10Hz-20MHz 1Vp-p signal into a buffer amplifier (10k|3pF input loading). First I thought of using a SPDT analog switch and resistor divider, but even 'low capacitance' devices come with 15~20pF capacitance on the common pin and have poor off isolation for my purpose. in --.--SW1--.--> to buffer | | 1kR | |--


LLC with an explicit discrete Lm

Started by Piotr Wyderski in sci.electronics.design3 years ago 15 replies

I need a number (~20) of fixed voltages in the range of 4-20V. Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small D class...

I need a number (~20) of fixed voltages in the range of 4-20V. Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small D class audio amplifier, 3.3V and 5V for logic and 10V for some auxiliary circuits. The input voltage is in the range of 10.8-15V, maybe 40W in total. Due to the number of output rails the complexity of the secondary sides does matter. This basically kil...


ENI Verteq VNA-1987 info

Started by artie in sci.electronics.design8 years ago 4 replies

Looking for operating info on an ENI Verteq VNA-1987-21121 amplifier. Operating manual, schematics, anything you've got. Yes, I tried...

Looking for operating info on an ENI Verteq VNA-1987-21121 amplifier. Operating manual, schematics, anything you've got. Yes, I tried Google, and it wasn't my friend on this one. Thanks and 73--


Transistor Conversion of Tube Amplifier

Started by Kevin Foster in sci.electronics.design6 years ago 15 replies

The circuit linked below appears to be a conversion of a three stage inverting tube amp tube to a transistor circuit, powered by...

The circuit linked below appears to be a conversion of a three stage inverting tube amp tube to a transistor circuit, powered by 3VDC. https://app.box.com/s/dwflbolnqe58ra9c1kssqjuq14dulxo0 It appears to be intended to capture high frequency ambient signals and re-broadcast them. It may also be designed to self-oscillate to add a carrier wave. In any case, I would like to build it o...


Application Note 948 - Linear Power Amplifier Using Complementary HEXFETs

Started by Anonymous in sci.electronics.design14 years ago 15 replies

Fascinating reading: http://www.irf.com/technical-info/appnotes/an-948.pdf (found from here: ...

Fascinating reading: http://www.irf.com/technical-info/appnotes/an-948.pdf (found from here: http://sound.westhost.com/articles/hexfet.htm) I've heard that the 2SK1058 is superior for audio, and is the only MOSFET spec'ed in Slone's book, but that this MOSFET is currently now unobtanium. What is the purpose of the inductor L1 (3 uH, air core) in series with the speaker? Any commen...