------------------LM13600_13700--------------- The LM13600/13700 was the result of a trip made to to an Electronic Organ manufacture. In those days Electronic Organ were primary analog. RCA had put out the 3080 transconductance and National Semiconductor was known for it ability to bomb the price on anything. ^ /_\ LM3080 __|_______________________ ___ | | | | | | Output -> <- -> <- |___| PNP\|___|/PNP PNP\|___|/PNP | _'| | |`_ _'| | |`_ | | |____| | |____| | | | | | | | <- | <- | |______|/PNP |______|/PNP | Control| |`_ | |`______| Current| | | | ^ | |____\ ________ | /_\ |_______ / | | _|_ | | | | / _ \ | | | | \/ \/ _ _| |__ _ | | /\_/\ | |_|' NPN NPN `|_| | | | \___/ |_| |`-> <-'| |_| | | | -IN |_______| +IN | | | | | | _|_ _| | _| | |________|' NPN _____|_|' NPN |___| | |`-> | |`-> IABI | ____| | ____| |_ | _| |_ | _| NPN `|_|_|' `|_|_|' NPN <-'| |`-> <-'| |`-> |_________| |_________| _|_ _|_ /// /// Gnd Gnd The design of RCA's 3080 did not need much improvement in that the control current had at least a 80dB dynamic range. It did make sense at the time to maybe do a stereo version since all audio signal processing was of course stereo. The design really started out as a just a practice layout for new mask designer. Bill Gross and myself spent about 5 minutes on the whole design. ^ /_\ LM13600 __|_______________________ ___ | | | | | | Output -> <- -> <- |___| PNP\|___|/PNP PNP\|___|/PNP | _'| | |`_ _'| | |`_ | | |____| | |____| | Buffer Input | | | | | ___ ^ | <- | <- | | | /_\ |______|/PNP |______|/PNP | |___| __|_ Control| |`_ | |`______| | _| | Current| | | | |_|' NPN_| ^ | |____\ ________ | |`->_|' 50X /_\ |_______ / | | | |`-> _|_ | | | | __| | / _ \ | | | | | | \/ \/ _ _| |__ _ | | | | /\_/\ | |_|' NPN NPN `|_| | | | | | \___/ |_| |`-> <-'| |_| | | | | | -IN |_______| +IN | | | _|_ | | | | | | | _|_ _| | _| | |___| | |________|' NPN _____|_|' NPN | Buffer |___| | |`-> | |`-> | Output IABI | ____| | ____| | |_ | _| ___ |_ | _| | NPN `|_|_|'___|' | `|_|_|' NPN | <-'| |`-> |`-> | <-'| |`-> | |_________|____| | |_________| | _|_ | _|_ | /// | /// | Gnd | Gnd | |__________________| First, the design was to be stereo. At that time we had a package where we could include a Darlington as an output buffer to save the customer money. Since the dynamic range of bias current was at least 80dB, the bias method shown above was chosen for the LM13600. At the time, the dynamic range was more like 100dB. The speed of the amplifier is greatly limited to 2MHz because of the lateral pnps. But this meant one could built a VCO or filter that could go from 10Hz to 1MHz. Today that range may be from 1Hz to MHz. ^ /_\ LM13700 __|_______________________ ___ | | | | | | Output -> <- -> <- |___| PNP\|___|/PNP PNP\|___|/PNP | _'| | |`_ _'| | |`_ | | |____| | |____| | Buffer Input | | | | | ___ ^ | <- | <- | | | /_\ |______|/PNP |______|/PNP | |___| __|_ Control| |`_ | |`______| | _| | Current| | | | |_|' NPN_| ^ | |____\ ________ | |`->_|' 50X /_\ |_______ / | | | |`-> _|_ | | | | __|_ | / _ \ | | | | |_ | | \/ \/ _ _| |__ _ | | 1X `|_| | /\_/\ | |_|' NPN NPN `|_| | | | <-'| | \___/ |_| |`-> <-'| |_| | | |_______| | -IN |_______| +IN | | _|_ | | | | | | _|_ _| | _| |___| | |________|' NPN _____|_|' NPN Buffer |___| | |`-> | |`-> Output IABI | ____| | ____| |_ | _| |_ | _| NPN `|_|_|' NPN NPN `|_|_|' NPN <-'| |`-> <-'| |`-> |_________| |_________| _|_ _|_ /// /// Gnd Gnd The main problem with the LM13600 method is the fact that the input transistor of the darlington moves with the control current. Not a very good thing for the audio application. Hence the LM13700 method shown above. ^ /_\ LM13600 __|_______________________ ___ | | | | | | Output -> <- -> <- |___| PNP\|___|/PNP PNP\|___|/PNP | _'| | |`_ _'| | |`_ | | |____| | |____| | Buffer Input | | | | | ___ ^ | <- | <- | | | /_\ Linear |______|/PNP |______|/PNP | |___| __|_ Diodes | |`_ | |`______| | _| | ___ | | | | |_|' NPN_| | | | |____\ ________ | |`->_|' 50X |___| |________ / | | | |`-> | | | | | __| | |______ | | | | | | | | | | | | | Control |_______\_ __\____ | | | _|_ Current | / / | | | | | | ^ | | | | | | | |___| /_\ _|_ | __| _|_ | | | Buffer _|_ \ / | | \ / | | | Output / _ \ _v_ NPN| | NPN _v_ | | | \/ \/ _|_ _| |__ _|_ | | | /\_/\ | |_|' `|_| | | | | \___/ |___| |`-> <-'| |___| | | | | -IN |____| + IN | | | | | | | | _|_ _| | _| | | |________|' NPN _____|_|' NPN | |___| | |`-> | |`-> | IABI | ____| | ____| | |_ | _| ___ |_ | _| | `|_|_|'___|' | `|_|_|' NPN | <-'| |`-> |`-> | <-'| |`-> | |_________|____| | |_________| | _|_ | _|_ | /// | /// | Gnd | Gnd | |__________________| Well, there was one more pin left over on each side of the stereo transconductance amplifier. That could not go to waste. So it was easy to simply add two linearizing diodes to each amplifier to predistort the input signal. Design done. No bread boards. Remember, this was just meant to give a new mask designer something to practice on. But after the layout, the design manager (Tim Isbell) say why not make it into a product? So we did, it came out working perfectly in that no changes where needed. Test system was easy DC. This product was trying to show us just how fast and cheaply it could be brought into production. This was the days when you could sample a product without a data sheet. It was already generating enough interest to spend some time on a datasheet. The Electronic Organ Companies where already giving us quite a few circuits. A few more circuits where developed to exploit the limits of the dynamic range. All application circuits were fired up. No problem. If every there was a IC that appeared to have a life of its own, the LM13600 did. It further when on to inspire the development of Delco's DNR project. I find it quite warming when I see magazines like "Popular Electronic" copy all my LM13600 data sheet work into a dedicated couple of transconductance articles. They seem to do this every couple of years. That says there are people out their who still love this kind of analog electronics. Don Sauer DSauerSanJose@aol.com