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The actual TTL threshold is two diode drops or 1.5V input and output depends on logic family drive current for a fanout of 10. … Fast forward 40 yrs to 74HCTxx and we have the same in/out threshold as TTL was but with rail to rail output. …

"TTL Levels" mean that the output is defined by TTL levels but is always driven by CMOS these days. But since CMOS levels are not universal, they still use TTL even though using CMOS to drive it. … TTL (Voh) means anything from 2 to 5V depending on load current but CMOS 74HCxxx CMOS at 5V is 50 (nom) ~100 Ohms (max) RdsOn so you can include this with your current limit calculations for 1.2V (@25' …

Rebar conducts but is also inductive ~ 0.5uH/m so if you have any grid transients nearby, you should add RF caps. It will also pickup AM signals. I suggest 100kHZ LPF. ESD and EMI ingress needs to b …

(Hex TTL BUffer) IOH = –3 mA for VOH= 2.4 min., 3.4 typ. … Thus ZOH the high level resistance is (4.5V-3.84V)/6mA = 110 ohms This is reduced for higher Vdd and rises for lower Vdd, unlike TTL. IOL = 6 mA for VOL = 0.33V max. …

A simple analog to logic converter uses the HC04 buffered inverter. (hex inverter CMOS) You can choose gain like Op Amp R ratio and AC couple to allow self-bias. e.g. C1= 0.1uF R1= 10K R2=1M Gain= …

74LS TTL input spec is basically the safe Vin(low) or Vil voltage with a 20k Pullup thru a diode. The 74HCxx family can certainly drive a lot more than 1 and possibly 10 LS04 TTL loads low "0". … =30 Not many designers will know or remember this, so let me tell everyone where TTL load power goes. …

I am not 100% sure they are TTL compatible precisely as TTL is strictly defined with a threshold of 1.5V or more likely it is CMOS with 2.5V threshold which can be TTL compatible but does not work when … This means your generator is poorly matched to your 2 loads Normally TTL can drive 10 loads or more and this does not seem to be the case. …

TTL went thru about 6 types of circuit design including the classic combinations of std (54/74) , low-power (54/74L) and Schottky (54/74LS,S). …

This 20 MHz resonance is due to your layout. For example with wire being 10nH/cm and twisted pair being 40~50 pF/m Hypothetically I can imagine your 20Mhz resonance caused by emissions, crosstalk …

Each and every TTL family had a fan out drive load of 10 units and most inputs were 1 unit in the same family. … Even though they make TTL compatible thresholds for CMOS with the “T” in 74HCT’ , one can also use a pullup R to Vcc from TTL to std. threshold 5V CMOS. …

As long as you give some margin below the MAX SAFE LEVELS , you are safe. that means .. +/- 50mA for output diode current and -.5 to 7.0 Vdc for Vout as long as above is observed, Running a …

While TTL has a standard current gain or “fanout” of 10 , “buffers” have more current drive depending on which buffer IC you can choose . … The actual threshold for ALL TTL families including 74HCT’ CMOS (TTL compatible) inputs is 1.3V+/- 0.1V typ for two Vbe diode drops. …

e.g. for Voh for TTL loads, Vcc=4.5V (5V-10%)Voh=3.98V Io =-4mA thus RdsOn=(4.5-3.98)/4mA= 520mV/4mA = 130 Ω (max) for Voh or output ="1" (Pch FET) e.g. for Vol for TTL loads, Vol= 0.26V/4mA = 65 Ω … (max) for Vol or output ="0" (Nch FET) Note that 74HCTxx series is designed to replace TTL IC's with a fanout of 10 loads so the input threshold is 1.5V instead of symmetrical Vcc/2. 74HCxxx is the …

For logic the critical factor is latency to reach switching threshold, which for TTL is actually 1.35V~1.4V or two Vbe drops, although 74HCT=1.5V approx. … So we can say Vdd/2 or Vcc/2 or 50%TTL, to mean CMOS logic but with the understanding that 74HC is different than 74HCT . …

This takes an understanding in Transmission Line Theory for full appreciation. But basically is not a problem for good layouts just a protection of reverse Vbe voltages on high speed bipolar devices f …